GIFT  OF 


1888  Die  Priifung  der  Chemischen  Beagentien 
auf  Beinheit.  Von  Dr.  C.  KRATJCH.  Pub- 
lished by  Julius  Springer,  Berlin. 

1891  Die  Priifung  der  Ckemischen  Beagentien 
auf  Beinheit.  Von  Dr.  C.  KRATJCH.  Pub- 
lished by  Julius  Springer,  Berlin. 

1896  Die  Priifung  der  Chemischen  Beagentien 
auf  Beinheit.  Von  Dr.  C.  KRAUCH.  Pub- 
lished by  Julius  Springer,  Berlin. 

1902  The  Testing  of  Chemical  Beagents  for 
Purity.  By  Dr.  C.  KRAUCH.  Translated  by 
J.  A.  WILLIAMS,  F.C.S.,  and  L.  W.  DUPR£, 
with  additions  and  emendations  by  the  author- 
(Translation  of  1896  Edition.)  Published  by 
Maclaren  &  Sons,  London. 

1905  Priifung  Der  Chemischen  Beagenzien  auf 
Beinheit.  Von  E.  MERCK.  Published  by 
E.  Merck,  Darmstadt. 

1907  Chemical  Beagents:  Their  Purity  and 
Tests.  By  E.  MERCK.  Authorized  translation 
by  HENRY  SCHENCK,  A.B.  (Translation  of 
1905  Edition.)  Published  by  D.  Van  Nostrand 
Co.,  New  York. 

1912  Priifung  der  Chemischen  Beagenzien  auf 
Beinheit.  (Zweite'Auflage.)  Von  E.  MERCK. 
Published  by  E.  Merck,  Darmstadt. 

1914     Chemical    Beagents:      Their    Purity     and 

Tests.  By  E.  MERCK.  Authorized  translation 
by  HENRY  SCHENCK,  A.  B.  (Translation  of 
1912  Edition.)  Published  by  Merck  &  Co., 
New  York.  Supplied  by  D.  Van  Nostrand  Co., 
New  York. 


CHEMICAL  REAGENTS 

THEIR  PURITY  AND  TESTS 


AUTHORIZED  TRANSLATION 
OF 

PRUFUNG  DER  CHEMISCHEN  REAGEflZIEN  AUF  REKHEIT 

(ZWEITE  AUFLAGE) 

VON 

E.   MERCK 


BY 

HENRY  SCHENCK,  A.B. (HARVARD) 


SECOND  EDITION,   REVISED 


MERCK   &   CO. 

NEW  YORK 
1914 


Copyright,  1914 

BY 

MERCK   &   CO. 


*  •»>• 

5  »J 


PRESS    OF 

BRAUNWORTH    &    CO. 

BOOK    MANLTACTURER8 

BROOKLYN.     N.     Y. 


TRANSLATOR'S  PREFACE 


The  second  edition  of  "  Priifung  der  chemischen  Reagenzien 
auf  Reinheit,"  presented  here  in  translation,  does  not  depart  essen- 
tially in  its  method  of  treatment  from  the  previous  one.  Since  the 
first  edition  of  the  work  appeared,  numerous  articles  have  come 
into  prominence  as  reagents,  however,  and  new  uses  have  been 
found  for  chemicals  long  part  of  the  laboratory  equipment,  so  that, 
besides  the  introduction  of  entirely  new  subjects,*  additions  and 
changes  have  also  been  made  in  the  text  of  the  earlier  edition. 
Frequently,  too,  these  changes  have  materially  raised  the  standard 
of  purity.  Coincident  with  this  improvement  is  the  inclusion 
among  the  references  of  important  new  contributions  upon  the  uses 
and  methods  of  testing  reagent  chemicals. 

There  have  also  been  made  several  deletions :  Acid  Oxalic 
Sublimed,  Indigotin,  Kassner's  Mixture,  and  a  few  of  the  less  impor- 


*  As  subjects  not  heretofore  treated  in  the  work  but  introduced  for  the 
first  time  in  this  edition,  may  be  mentioned  the  following: 

Alphanaphthylamine,  Ammonium  Chromate,  Ammonium  Molybdate 
Solution,  Ammonium  Persulphate,  Benzidine  for  Blood  Test,  Bismuth  and 
Potassium  Iodide  Solution, 'Carbon  Tetrachloride,  Carmine-Fibrin,  Chromium 
Trioxide  for  Carbon  Determination,  Cobalt  Nitrate,  Free  from  Nickel,  Cobalt 
Oxide,  Copper  Hydroxide,  Copper  Oxide-Asbestos,  Devarda's  Metal,  Dicyandi- 
amidine  Sulphate,  Dimethylglyoxime,  Dimethylparaphenylenediamine  Hydro- 
chloride,  Ferric  Oxide,  Glass  Wool,  Hydrazine  Sulphate,  Indigo  Carmine, 
Indigo  Solutions,  Lead  Peroxide  Granulated,  Magnesia  Mixture,  Magnesite, 
Manganese  Metaphosphate  Solution,  Methyl  Red,  Platinized  Pumice  Stone, 
Poirrier's  Blue  C4B,  Potassium  Persulphate,  Quartz  Sand,  Sea  Sand,  Silver- 
Asbestos,  Sodium-Cobaltic  Nitrite  Solution,  Tetramethylparaphenylenediamine 
Hydrochloride,  Yellow  Oxide  of  Mercury. 


361296 


vi  TRANSLATOR'S  PREFACE 

tant  dilutions  of  the  acids  have  been  deleted.  Gallein,  Dry,  has  taken 
the  place  of  Gallein,  Liquid.  The  tables  of  equivalents  of  standard 
solutions  have  been  replaced,  in  response  to  a  suggestion,  by  a  table 
giving  approximate  strengths  and  brief  directions  for  the  prepara- 
tion of  solutions  for  reagent  purposes,  compiled  from  published 
writings. 

In  adapting  the  standards  to  the  needs  of  American  chemists, 
furthermore,  it  has  been  necessary  in  several  cases  to  deviate  from 
the  German  standard  in  the  translation.  Instances  of  such  changes 
are  the  tests  for  tartaric  acid  in  citric  acid  and  in  succinic  acid, 
for  silicofluoride  in  ammonium  fluoride,  for  hydriodic  acid  in  hydro- 
bromic  acid,  etc.;  more  or  less  complete  revision  is  to  be  found 
in  the  texts  of  Acid  Hydrochloric,  Acid  Nitric,  etc. 

Another  feature  introduced  in  this  translation  is  the  parenthetical 
statement  appended  to  each  test  giving  in  terms  of  percentage  the 
minimum  amount  of  the  impurity  which  would  be  recognized  by 
the  test.*  In  many  cases  where  gravimetric  or  volumetric  deter- 
minations are  made,  these  percentage  figures  are,  of  course,  exact. 
In  other  cases,  however,  the  qualitative  tests  had  in  a  certain  sense 
to  be  given  a  quantitative  value,  which  had  to  be  determined  by 
experiments:  Known  quantities  of  an  impurity  were  put  into 
the  chemical  or  its  solution,  and  gradually  added  to  until  the  given 
qualitative  test  for  that  impurity  showed  a  reaction. 

The  figures  thus  obtained  for  qualitative  tests  are  by  no  means 
to  be  considered  final,  as  they  depend  to  an  extent  on  delicacy  of 
manipulation;  on  the  interpretation  of  such  terms  as  "  faint," 
"  slight,"  "  cloudy,"  etc.;  and  also  on  the  absence  of  other  impurities, 
the  presence  of  which  might  conceivably  alter  them.  Yet,  taken 
by  and  large,  they  will  give  a  more  definite  idea  of  the  chemicals 
that  conform  to  the  tests  laid  down;  and,  furthermore,  they  will 
and  do  sometimes  in  most  striking  fashion  show  the  delicacy  or 
lack  of  it  of  some  of  the  tests.  Thus  they  carry  a  two-fold  pos- 


*  When  impurities  are  tested  for  not  singly  but  as  classes — as  for  instance 
"  heavy  metals,"  "  aldehydes,"  etc.,— a  definite  percentage  statement  becomes 
obviously  impossible.  Also,  when  the  text  confines  the  test  with  H2S  for  heavy 
metals  to  either  alkaline  or  acid  solution,  the  statement  as  to  the  absence  of 
heavy  metals  relates  necessarily  to  their  absence  in  the  prescribed  solution  only. 


TRANSLATOR'S  PREFACE  vii 

\    v" 

sibility— that  of  pointing  the  way  to  improvements  in  both  chem- 
icals and  tests. 

While  these  are  being  worked  out,  however,  the  parenthetical 
percentage  statements  will,  in  the  meantime,  prove  of  use  to  the 
analyst  when  he  selects  reagents  for  particular  purposes,  estimates 
the  relative  value  of  tests,  or  makes  allowances  and  corrections 
in  his  findings  or  in  those  of  his  assistants  or  students. 

THE  TRANSLATOR. 

NEW  YORK, 

April  15,  1914. 


TRANSLATOR'S  NOTE 


For  the  sake  of  brevity,  expressions  throughout  the  book  are 
sometimes  used  without  full  qualification.  The  following  is  then 
to  be  their  interpretation: 

Atomic  Weights,  Quantitative  Calculations,  etc.,  are  based  on 
the  table  of  International  Atomic  Weights  for  1913  in  which  O  =  16. 

Specific  Gravities  are  given  at  +15°  C.  compared  with  water 
at  +15°  C.  When  a  specific  gravity  is  given  with  only  two  decimal 
places,  it  is  understood  that  a  variation  in  the  third  decimal  is 
permissible. 

UnweigVable  Residue  or  words  to  that  effect  apply  to  residues 
weighing  0.0005  gm.  or  less.  In  residue  determinations  when 
filtration  is  employed,  ashless  filters  are  to  be  used  in  collecting 
residues  for  ignition. 

Solutions  o'f  chemicals  to  be  tested,  in  the  absence  of  specific 
directions  for  their  preparation,  are  made  from  1  gm.  diluted  to  20 
c.c.  or  proportionately. 

Parts  by  Weight  are  to  be  understood  when  the  term  "  parts  " 
is  used  or  implied.  For  instance,  the  expression  1  : 20  means  1  gm. 
+  19  gm. 

Volumetric  Determinations  can  of  course  be  made  with  other 
solutions  than  the  potassium  hydroxide  and  hydrochloric  acid 
solutions  generally  selected,  provided  they  be  equivalent.  In  such 
substitution,  however,  due  regard  must  be  given  to  the  suitable- 
ness of  the  indicator. 

The  Boiling-point  of  a  substance  is  affected  by  variation  in 
atmospheric  pressure,  and  this  fact  must  be  taken  into  account 
when  the  boiling-point  is  employed  as  a  test  of  purity. 

viii 


TRANSLATOR'S  NOTE  ix 

Nitric  Acid  has  a  specific  gravity  of  1.153. 

Hydrochloric  Acid,  one  of  1.124. 

Ammonia  Water,  that  of  0.96. 

The  Marsh  Apparatus  should  be  set  up  with  a  200  c.c.  generating 
flask. 

The  tests  presuppose  the  use  of  Jena  or  some  equally  resistant 
Glassware. 

The  abbreviations  of  the  names  of  periodicals  in  the  references 
are  those  commonly  used  in  abstracts  in  American  journals. 


CHEMICAL    REAGENTS 


ACETONE 
(CH3)2CO.     Mol.  Wt.  58.04 

A  clear,  colorless  liquid,  boiling  at  55°  to  56°  C.,  and  having 
a  specific  gravity  of  0.798. 

TESTS   OF  PURITY 

Residue  on  Evaporation.  —  25  c.c.  of  acetone  on  evaporation  should  leave 
no  weighable  residue.  (Indicating  less  than  0.0025  per  cent.) 

Acids.  —  Acetone  should  not  redden  blue  litmus  paper.  (Indicating  none 
present.) 

Solubility  in  Water.  —  Acetone  should  be  miscible  with  an  equal  volume  of 
water,  yielding  a  clear  liquid. 

Aldehydes.  —  On  heating  10  c.c.  of  acetone  with  5  c.c.  of  ammoniacal  silver 
nitrate  solution*  (protected  from  the  light)  for  fifteen  minutes  on  a  water- 
bath  of  about  50°  C.,  the  mixture  must  not  acquire  a  brown  color,  and  no 
metallic  silver  should  deposit.  (Indicating  none  present.) 

Substances  Oxidizable  by  Permanganate.  —  On  adding  one  drop  of  a 
1  :  1000  solution  of  potassium  permanganate  to  10  c.c.  of  acetone,  and  main- 
taining a  temperature  of  not  over  15°  C.,  the  pink  color  should  not  be  entirely 
discharged  within  fifteen  minutes.  (Indicating  none  present.) 

Water.  —  On  mixing  equal  volumes  of  acetone  and  petroleum  benzin  (boiling- 
point  40°  to  70°  C.),  two  layers  should  not  be  formed.  (Indicating  less  than  3 
per  cent.) 

NOTE.  —  Regarding  the  quantitative  determination  of  acetone,  see  G.  Lunge, 
Chem.-Tech.  Untersuch.-Meth.,  6  ed.,  3,  114  and  924  (1911).  Compare  Allen's 
Commercial  Organic  Analysis,  4  ed.,  1,  100  (1909).  See  also  G.  Kramer,  Ber., 
13,  1000  (1880);  abst.,  J.  Chem.  Soc.,  38,  826  (1880).  J.  Messinger,  Ber.,  21. 
3366  (1888);  abst.,  J.  Chem.  Soc.,  56,  313  (1889).  H.  Strache,  Monatsh.  Chem., 
12,  524  (1891)  [or  Z.  anal.  Chem.,  31,  573  (1892)];  abst.,  J.  Chem.  Soc.,  62, 
546  (1892).  F.  Robineau  and  G.  Rollin,  Z.  anal.  Chem.,  33,  87  (1894);  abst., 
J.  Chem.  Soc.,  64,  II,  556  (1893). 


*  The  ammoniacal  silver  nitrate  solution  is  made  by  mixing  10  c.c.  of  silver 
nitrate  solution  (1  :  20)  with  5  c.c.  of  ammonia  water  (10  per  cent). 

1 


2  ?*VBlfflfC!AL  REAGENTS 

ACID    ACETIC 

HC2H3O2.    Mol.  Wt.  60.03 

I 
ACID  ACETIC,   99.5  PER  CENT 

A  clear,  colorless  liquid,  with  a  strong  odor;  miscible  in  all  pro- 
portions with  water  or  alcohol,  and  containing  at  least  99.5  per  cent 
of  HC2H302.  Specific  gravity  about  1.048  at  25°  C.  At  about 
+15.65°  C.  it  solidifies. 

TESTS  OF  PURITY 

Non-volatile  Matter.  — 100  c.c.  of  acetic  acid  should  leave  no  weighable 
residue  on  evaporation  and  ignition.  (Indicating  less  than  0.00048  per  cent.) 

Hydrochloric  Acid.  —  5  c.c.  of  acetic  acid  diluted  with  50  c.c.  of  water  should 
not  be  changed  on  the  addition  oi  5  c.c.  of  nitric  acid  followed  by  silver  nitrate 
solution.  (Indicating  less  than  0.0003  per  cent  Cl.) 

Sulphuric  Acid.  —  Add  to  100  c.c.  of  acetic  acid  a  small  amount  of  sodium 
carbonate  insufficient  to  make  alkaline,  evaporate  the  solution  to  dryness,  take 
up  the  residue  with  50  c.c.  of  water,  and  add  barium  chloride  solution.  No  weigh- 
able precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (I  .di- 
c.iting  not  more  than  0.00016  per  cent  SO3.) 

Heavy  Metals.  —  (a)  A  mixture  of  20  c.c.  of  acetic  acid  and  100  c.c.  of 
water  should  not  be  affected  by  passing  through  it  a  current  of  hydrogen 
sulphide  gas.  (Indicating  none  present.) 

(6)  Evaporate  100  c.c.  of  the  acid  to  a  small  volume,  add  a  slight  excess  of 
ammonia  water,  and  dilute  with  water  to  a  100  c.c.  A  green  or  dark  color  should 
not  develop  on  adding  a  few  drops  of  ammonium  sulphide  solution.  (Indicating 
none  present.) 

Iron.  —  12.5  c.c.  of  the  acid  diluted  with  an  equal  volume  of  water  and  boiled 
after  adding  a  few  drops  of  nitric  acid,  should  not  develop  a  red  color  on  addition 
of  potassium  sulphocyanate  solution.  (Indicating  less  than  0.0001  per  cent  Fe.) 

Formic  and  Sulphurous  Acids.  —  2  c.c.  of  the  acid  are  just  neutralized  with 
ammonia  water  and  a  little  silver  nitrate  solution  is  added.  No  dark  color 
or  deposit  should  appear  on  boiling  two  minutes.  (Indicating  less  than  0.05  per 
cent  SO2,  or  less  than  0.4  per  cent  HCOOH.) 

Substances  Reducing  Permanganate.  —  2  c.c.  of  the  acid  are  diluted  with  10 
c.c.  of  water  and  0.1  c.c.  of  decinormal  solution  of  potassium  permanganate  added. 
The  pink  color  should  not  be  entirely  changed  to  brown  within  two  hours.  (Indi- 
cating none  present.) 

Other  Empyreumatic  Bodies.  —  No  smoky  color  should  be  noticeable  upon 
making  10  c.c.  of  the  acid  alkaline  with  solution  of  potassium  hydroxide.  (Indi- 
cating none  present.) 

Earths.  —  10  c.c.  of  acetic  acid  diluted  with  100  c.c.  of  water  and  treated  with 
an  excess  of  ammonia  water,  should  not  become  turbid  on  adding  ammonium 
oxalate  solution.  (Indicating  less  than  0.003  per  cent  earths  as  Ca.) 

Quantitative  Determinations.  —  Dilute  5  gm.  of  acetic  acid  with  sufficient 
water  to  make  50  c.c.  Titrate  10  c.c.  of  this  solution  with  normal  potassium 
hydroxide  solution,  using  phenolphthalein  as  the  indicator.  At  least  16.5  c.c. 


ACID  ACETIC 


of  the  normal  potassium  hydroxide  solution  should  be  required  to  produce  the 
pink  color. 

1  c.c.  of  normal  KOH  =  0.06003  gm.  HC2H3O2,  log.  77837. 

The  acetic  acid  content  may  also  be  ascertained  from  the  congealing-point,* 
or  from  the  specific  gravity  if  due  note  be  taken  of  the  fact  that  the  specific 
gravities  above  1.0553  represent  in  each  case  two  liquids  of  different  acetic  acid 
content,  f 

II 
ACID  ACETIC,   GLACIAL,  96  PER  CENT 

A  clear,  colorless  liquid  with  a  strong  odor;  congealing  at  about 
10°  C.,  having  a  specific  gravity  of  at  most  1.064  and  boiling  at 
110°-119°  C.  It  contains  at  least  96  per  cent  of  HC2H302. 

TESTS   OF  PURITY 

The  tests  of  purity  and  the  quantitative  determination  are  to  be  carried 
out  as  described  under  Acid  Acetic,  99.5  per  cent,  observing  the  conditions  there 
given. 

Ill 
ACID  ACETIC,  90  PER  CENT 

A  colorless  liquid  having  a  specific  gravity  1.071  and  containing 
at  least  90  per  cent  of  HC2H302. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Acid  Acetic,  99.5  per  cent,  observ- 
ing the  conditions  there  described. 

IV 
ACID   ACETIC,   36  PER  CENT 

A  clear,  colorless  liquid,  specific  gravity  about  1.048,  and  con- 
taining about  36  per  cent  of  HC2H3O2. 

TESTS   OF  PURITY 

The  tests  of  purity  and  details  of  execution  are  the  same  as  those  given  under 
Acid  Acetic,  99.5  per  cent.  But  instead  of  1  gm.  (or  c.c.)  of  99.5  per  cent, 
use  2.5  gm.  (or  c.c.)  of  the  36  per  cent  acid. 


*  See  Lunge,  Chem.-Tech.  Untersuch.-Meth.,  5  ed.,  3,  934  (1905).  Compare 
Landolt-Bornstein-Roth,  Physikalisch-Chemische  Tabellen,  4  ed.,  296  (1912). 

f  Compare  Lunge,  Chem.-Tech.  Utersuch.-Meth.,  6  ed.,  3,  954  (1911).  Also 
U.  S.  Pharmacopoeia,  VIJI,  p,  610  (1905).  Landolt-Bornstein-Roth,  loc.  cit. 


4  CHEMICAL  REAGENTS 

ACID  ACETIC,  DILUTED,  30  PER  CENT 

A  colorless  liquid  having  the  specific  gravity  1.040-1.042.     The 
liquid  contains  about  30  per  cent  of  HC2H302. 
TESTS  OF  PURITY 

The  tests  to  be  made  are  those  given  under  Acid  Acetic,  99.5  per  cent,  observ- 
ing the  conditions  there  described.  But  instead  of  1  gm.  or  c.c.  of  the  99.5  per 
cent,  use  3  gm.  or  c.c.  of  the  30  per  cent  acid. 

(ACID)   ACETIC  ANHYDRIDE 
(CH3CO)2O.    Mol.  Wt.  102.05 

A  colorless  liquid  of  pungent  odor,  boiling  at  about  137°  C. 
Specific  gravity  1.080  to  1.085. 

On  pouring  acetic  anhydride  into  water,  it  does  not  at  first 
mix  with  the  latter,  but  sinks  to  the  bottom  of  the  vessel.  Gradually, 
however,  it  dissolves,  forming  acetic  acid. 

TESTS  OF  PURITY 

Hydrochloric  Acid.  —  1  c.c.  of  acetic  anhydride  dissolved  in  50  c.c.  of  water, 
and  acidulated  with  5  c.c.  of  nitric  acid  (sp.gr.  1.15),  should  show  at  most  a 
slight  opalescence  with  silver  nitrate  solution.  (Indicating  less  than  0.002 
per  cent  Cl.) 

Non-volatile  Matter.  —  10  c.c.  of  acetic  anhydride  should  leave  no  weighable 
residue  on  evaporation.  (Indicating  less  than  0.005  per  cent.) 

Quantitative  Determination.  —  Dissolve  5  gm.  of  acetic  anhydride  in  water 
and  dilute  to  50  c.c.  Titrate  10  c.c.  of  this  solution  with  normal  potassium 
hydroxide  solution,  using  phenolphthalein  as  indicator.  It  should  require  at 
least  19.3  c.c.  of  the  normal  potassium  hydroxide  solution  to  develop  the  pink  color. 

1  c.c.  of  normal  KOH  =  0.051025  gm.  of  (CH3CO)2O,  log.  70778. 

(ACID)   BORIC  ANHYDRIDE 

(Boron  Trioxide;  Boric  Acid,  Fused) 
B2O3.    Mol.  Wt.  70.0. 

Brittle,  vitreous,  hygroscopic  lumps.  Used  in  silicate  analyses, 
according  to  Jannasch.* 

TESTS   OF  PURITY 
Silica,  Alkalies,  etc. —  Add  50  c.c.  of  methyl  alcohol-hydrochloric  acidf  to 

*  References:  P.  Jannasch  and  O.  Heidenreich.  Ztschr.  anorgan.  Chem  12, 
211  (1896)  [or  Ztschr.  anal.  Chem.,  36,  382  (1897)];  abst.,  J.  Chem.  Soc.,  70,  II, 
576  (1896). 

fThe  methyl  alcohol-hydrochloric  acid  is  prepared  by  saturating  pure, 
anhydrous  methyl  alcohol,  keeping  the  temperature  low,  with  thoroughly  dried 


ACID  CARMINIC 


5  gm.  of  the  powdered  boric  anhydiide*  in  a  weighed  platinum  dish,  stir  with 
a  platinum  wire  until  completely  dissolved,  and  evaporate  the  liquid  over  a 
small  flame,  the  platinum  dish  being  placed  on  wire  gauze.  If  a  residue  remains, 
it  is  treated  anew  with  25  c.c.  of  the  methyl  alcohol-hydrochloric  acid,  the  liquid 
evaporated,  and  the  dish  and  contents  gently  ignited.  There  must  remain  no 
weighable  residue. f  (Indicating  less  than  0.01  per  cent.) 


ACID   CARMINIC  t 
Mol.  Wt.  494.16 


Purple-brown,  amorphous  masses,  affording  a  dark  red  powder 
on  trituration.  Carminic  acid  is  easily  soluble  in  water  and  in 
alcohol,  but  is  insoluble  in  benzene  and  chloroform.  It  has  no 
constant  melting-point. 

TESTS  OF  PURITY 

Solubility.  —  1  gm.  of  carminic  acid  dissolves  completely  in  2  c.c.  of  water. 
The  addition  of  20  c.c.  of  90  per  cent  alcohol  to  this  solution  should  cause  no 
appreciable  precipitation. 

If  the  carminic  acid  is  intended  to  be  used  as  an  indicator  in  acidimetry, 
it  must  first  be  tested  as  to  its  sensitiveness,  as  follows: 

Dissolve  1  gm.  of  the  carminic  acid  in  100  c.c.  of  water  and  add  one  drop 
of  this  solution  to  a  solution  of  5  gm.  of  ammonium  chloride  in  50  c.c.  of  water. 
The  addition  to  this  latter  solution  of  one  drop  of  decinormal  potassium  hydroxide 
solution  should  cause  a  change  in  color  from  yellowish-red  to  violet-red. 


hydrochloric  acid  gas  (prepared  most  readily  by  dropping  concentrated  sulphuric 
acid  into  concentrated  hydrochloric  acid).  On  standing  for  some  time,  however, 
the  methyl  alcohol-hydrochloric  acid  loses  its  original  effectiveness. 

*  The  powdering  must  be  done  in  an  agate  mortar,  since  the  rubbing  up  of 
hard  pieces  of  the  anhydride  in  porcelain  or  other  mortars  is  apt  to  introduce 
impurities  into  the  chemical. 

t  If  a  residue  remains  after  the  second  treatment  with  methyl  alcohol- 
hydrochloric  acid  and  ignition,  repeat  the  entire  operation  a  third  time  in  order 
to  make  sure  it  is  not  some  of  the  anhydride  still  un volatilized. 

|  References:  E.  Schunck  and  L.  Marchlewski,  Ber.,  27,  2979  (1894);  abst., 
J.  Chem.  Soc.,  68,  I,  67  (1895).  C.  Liebermann  and  H.  Voswinckel,  Ber.,  30, 
688  (1897);  abst.,  J.  Chem.  Soc.,  72,  I,  292  (1897).  Ber.,  30,  1731  (1897); 
abst.,  J.  Chem.  Soc.,  72,  I,  539  (1897).  C.  Liebermann,  P.  Horing,  and  F. 
Wiedemann,  Ber.,  33,  149  (1900);  abst.,  J.  Chem.  Soc.,  78,  1,236  (1900).  J. 
Landau,  Ber.,  33,  2446  (1900);  abst.,  J.  Chem.  Soc.,  78,  661  (1900);  C.  Lieber- 
mann and  J.  Landau,  Ber.,  34,  2153  (1901);  abst.,  J.  Chem.  Soc.,  80,  I,  545 
(1901).  C.  Liebermann  and  S.  Lindenbaum,  Ber.,  35,  2910  (1902);  abst.,  J. 
Chem.  Soc.,  82,  I,  787  (1902).  O.  Dimroth,  Ber.,  42,  1611,  1735  (1909);  abst.t 
J.  Chem.  Soc.,  96,  I,  485  (1909). 

Regarding  the  use  of  carminic  acid  as  a  reagent  see  T.  J.  Bogomoloff  and 
N.  J.  Wassilieff,  Petersburger  med.  Wochschr.,  294  (1897);  absL,  E.  Merck, 
Annual  Report,  27  (on  year  1898).  Compare  Pharm.  Zentralhalle,  40, 120  (1899). 


6  CHEMICAL  REAGENTS ' 

ACID  CITRIC 

C6H8O7+H2O.    Mol.  Wt.  210.08 

Colorless,  odorless,  rhombic  prisms,  efflorescing  superficially  in 
warm  air. 

Citric  acid  is  soluble  in  0.75  part  of  cold  and  in  0.5  part  of 
boiling  water;  in  1  part  of  alcohol  (about  85  per  cent  by  weight), 
and  in  50  parts  of  ether. 

TESTS  OF  PURITY 

Oxalic  Acid.  —  On  dissolving  10  gm.  of  citric  acid  in  20  c.c.  of  water,  and 
adding  5  c.c.  of  a  1:2  potassium  acetate  solution  and  50  c.c.  of  85  per  cent 
alcohol,  no  turbidity  should  be  produced  within  two  hours. 

Tartaric  Acid*  and  Sugar.  —  1  gm.  of  citric  acid  and  10  c.c.  of  sulphuric 
acid  (sp.gr.  1.84)  are  triturated  in  a  porcelain  mortar  previously  rinsed  with 
sulphuric  acid.  When  this  mixture  is  then  heated  in  a  test-tube  for  an  hour 
in  a  boiling  water-bath  it  acquires  at  most  a  slight  yellow  color,  but  no  brown 
color  should  develop.  (Indicating  less  than  1  per  cent  C4H6O6,  and  less  than  0.05 
per  cent  saccharose.) 

Sulphuric  Acid.  —  20  c.c.  of  the  1  :  10  aqueous  solution  must  show  no  change 
on  adding  barium  chloride  solution  and  allowing  to  stand  fifteen  hours.  (Indicat- 
ing less  than  0.002  per  cent  SO3.) 

Calcium.  —  20  c.c.  of  the  1  :  10  aqueous  solution  must  show  no  change  on 
the  addition  of  ammonium  oxalate  solution.  (Indicating  less  than  0.01  per 
cent  Ca.) 

Lead.f  —  A  solution  of  5  gm.  of  citric  acid  in  10  c.c.  of  water,  to  which  12 
c.c.  of  ammonia  water  are  added,  should  not  acquire  a  dark  color  upon  adding 
hj'drogen  sulphide  water.  (Indicating  less  than  0.001  per  cent  Pb.) 

Non-volatile  Matter.  —  1  gm.  of  citric  acid  must  leave  no  weighable  residue 
on  ignition.  (Indicating  less  than  0.05  per  cent.) 

Quantitative  Determination.  —  On  dissolving  1  gm.  of  citric  acid  in  30  c.c. 
of  water  and  titrating  with  normal  potassium  hydroxide  solution,  using  phenol- 
phthalein  as  indicator,  not  less  than  14.2  c.c.  of  the  alkali  solution  should  be 
required  to  develop  the  pink  color. 

1  c.c.  of  normal  KOH  =0.07002  gm.  of  C6H8O7+H20,  log.  84522. 

ACID   GALLIC 
C7H6O5  +H2O.     Mol.  Wt.  188.06. 

Colorless  or  slightly  yellowish  needles  or  prisms,  which  melt 
and  slowly  decompose  at  220°  C.  Gallic  acid  dissolves  in  85  parts 


*  For  detection  of  tartaric  acid  in  citric  acid  see  Cailletet,  Arch.  Pharm.  (3), 
13,  468  (1878);  abst.  Chem.  Zentrbl.  (3)  10,  14,  (1879);  abst.,  J.  Chem.  Soc.,  35, 
674  (1879).  M.  L.  Crismer,  Bull.  Soc.  Chim.  Paris,  '(3),  6,  23  (1891);  abst.,  J. 
Chem.  Soc.,  62,  546  (1892).  Salzer,  Chem.  Zentr.  (3),  19,  1244  (1888);  abst., 
J.  Chem.  Soc.,  54,  996  (1888).  O.  Spindler,  Chem.  Ztg.,  28,  15  (1904);  abst. 
Chem.  Zentr.  (5),  8,  696  (1904);  abst.,  J.  Chem.  Soc.,  86,  II,  152  (1904). 

t  Regarding  the  examination  of  citric  acid  for  lead  compounds  see  M.  Bucket, 
Z.  anal.  Chem.,  32,  465  (1893);  abst.,  J.  Chem.  Soc.,  64,  II,  557  (1893).  Tatlock 
and  Thompson,  Analyst,  33,  173  (1908);  abst.,  C.  A.,  2,  2269  (1908). 


ACID  HYDRIODIC 


of  cold  water,  in  3  parts  of  boiling  water,  and  in  about  6  parts  of 
95  per  cent  alcohol.     In  ether*  (sp.gr.  0.72)  it  is  difficultly  soluble. 

TESTS   OF  PURITY 

Solubility  in  Water.  —  1  gm.  of  gallic  acid  must  dissolve  completely  in  20 
c.c.  of  water  on  heating.  The  solution  must  be  colorless  or  only  very  faintly 
yellowish. 

Water  Content.  —  On  drying  1  gm.  of  gallic  acid  at  100°  C.  to  constant 
weight,  it  should  not  lose  more  than  0.10  gm.  in  weight.  (Indicating  not  more 
than  10  per  cent.) 

Sulphuric  Acid.  —  On  adding  1  c.c.  of  hydrochloric  acid  and  some  barium 
chloride  solution  to  a  hot  1  :  50  aqueous  solution  of  gallic  acid,  a  precipitate 
of  barium  sulphate  must  not  be  visible  after  standing  one  hour  at  about  50°  C. 
(Indicating  less  than  0.005  per  cent  SO3.) 

Inorganic  Matter.  —  1  gm.  of  gallic  acid  must  leave  no  weighable  residue 
on  ignition.  (Indicating  less  than  0.05  per  cent.) 


ACID   HYDRIODIC 

HI.     Mol.  Wt.  127.93 

I 
ACID    HYDRIODIC,  Sp.  Gr.  1.50 

A  clear,  colorless  liquid  which,  on  exposure  to  light  and  air, 
rapidly  becomes  yellow  to  brown,  due  to  the  separation  of  iodine. 
Specific  gravity  1.50.  The  liquid  contains  about  43  per  cent  of  HI. 

TESTS   OF  PURITY 

Non-volatile  Matter  and  Phosphorus.  —  5  gm.  of  hydriodic  acid  should  not 
leave  more  than  0.002  gm.  residue  on  evaporation.  Upon  gentle  ignition  the 
residue  should  not  burn  (indicating  no  phosphorus  present),  and  after  the  ignition 
no  weighable  residue  should  remain.  (Indicating  less  than  0.01  per  cent  non- 
volatile matter.) 

Sulphuric  Acid.  —  On  diluting  3  c.c.  of  hydriodic  acid  with  50  c.c.  of  water 
and  adding  barium  chloride  solution,  no  barium  sulphate  should  precipitate 
on  standing  fifteen  hours.  (Indicating  less  than  0.01  per  cent  SO3.) 

Heavy  Metals  and  Earths.  —  On  diluting  10  c.c.  of  hydriodic  acid  with  100 
c.c.  of  water  and  passing  hydrogen  sulphide  gas  into  it  no  dark-colored  precipitate 
should  form;  then  after  adding  an  excess  of  ammonia  water  and  some  ammonium 
sulphide  solution  neither  a  green  color  nor  a  precipitate  should  be  visible.  (Indi- 
cating no  heavy  metals  present.)  Three  c.c.  of  the  hydriodic  acid  diluted  with 

*  The  solubility  of  gallic  acid  in  ether  depends  very  largely  on  the  amount 
of  alcohol  in  the  ether. 


CHEMICAL  REAGENTS 


30  c.c.  of  water  and  made  alkaline  with  ammonia  water  should  show  no  change 
upon  the  addition  of  ammonium  oxalate  solution.  (Indicating  less  than  0.005 
per  cent  earths  as  Ca.) 

Hydrochloric  and  Hydrobromic  Acids.  —  Dilute  1  gm.  of  hydriodic  acid  with 
20  c.c.  of  water,  add  an  excess  of  silver  nitrate  solution  followed  by  30  c.c.  of 
ammonia  water,  shake  well,  and  filter.  On  acidulating  the  filtrate  with  nitric 
acid,  only  a  slight  turbidity  may  develop,  never  a  precipitate.*  (Indicating 
less  than  0.002  per  cent  as  Cl.) 

Quantitative  Determination.  —  Dilute  5  gm.  of  hydriodic  acid  with  50  c.c. 
of  water  and  titrate  with  normal  potassium  hydroxide  solution,  using  methyl 
orange  as  an  indicator.  At  least  17  c.c.  of  the  normal  alkali  solution  must 'be 
required  to  effect  the  change  in  color. 

1  c.c.  of  normal  KOH  =  0.12793  gm.  of  HI,  log,  10697. 


II 
ACID   HYDRIODIC,  Sp.  Gr.  1.70 

A  yellowish  or  brownish  liquid  of  specific  gravity  1.70.  The  acid 
contains  about  57  per  cent  of  HI,  and  is  used  for  methoxyl  deter- 
mination, according  to  Zeisel. 

TESTS   OF  PURITY 

Tests  for  non-volatile  impurities  and  sulphuric  acid  are  to  be  made,  observing 
the  conditions  given  under  Acid  Hydriodic,  Sp.Gr.  1.50.  In  titrating  this  acid, 
phenolphthalein  is  used  as  the  indicator. 

ACID   HYDROBROMIC 
HBr.     Mol.  Wt.  80.93 

A  clear,  colorless,  or  faintly  yellowish  liquid,  of  specific  gravity 
1.38.  It  contains  about  40  per  cent  of  HBr. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  10  gm.  of  hydrobromic  acid  on  evaporation  on  the 
water-bath  should  leave  not  more  than  0.001  gm.  of  residue.  (Indicating  not 
more  than  0.01  per  cent.) 

Arsenic.  —  A  mixture  of  1  c.c.  of  hydrobromic  acid  and  3  c.c.  of  stannous 
chloride  solution  should  show  no  dark  color  in  one  hour.  (Indicating  less  than 
0.0015  per  cent  As.) 

Sulphuric  Acid.  —  On  diluting  5  c.c.  of  hydrobromic  acid  with  50  c.c.  of  water 
and  adding  barium  chloride  solution,  a  precipitate  of  barium  sulphate  should  not 
form  on  standing  fifteen  hours.  (Indicating  less  than  0.0075  per  cent  SO3.) 


*  A  slight  turbidity  is  permitted,  because  silver  iodide  is  not  absolutely 
insoluble  in  ammonia  water. 


ACID  HYDROCHLORIC 


Heavy  Metals.  —  (a)  Dilute  10  c.c.  of  hydrobromic  acid  with  40  c.c.  of 
water  and  introduce  hydrogen  sulphide  gas.  No  change  should  appear.  (Indi- 
cating none  present.) 

(&)  Dilute  10  c.c.  of  hydrobromic  acid  with  10  c.c.  of  water,  and  add  15 
c.c.  of  ammonia  water,  followed  by  a  few  drops  of  ammonium  sulphide  solution. 
Neither  a  brown  coloration  nor  a  precipitate  should  appear.  (Indicating  none 
present.) 

(c)  Dilute  5  c.c.  of  hydrobromic  acid  with  25  c.c.  of  water  and  add  potassium 
sulphocyanate  solution.  No  reddish  coloration  should  occur.  (Indicating  less 
than  0.00015  per  cent  Fe.) 

Hydrochloric  Acid.  —  0.2  c.c.  of  hydrobromic  acid  are  diluted  with  4  c.c. 
of  water,  and  then  mixed  with  15  c.c.  of  decinormal  silver  nitrate  solution.  To 
this  mixture  add  6  c.c.  of  ammonium  carbonate  solution  (1  part  of  ammonium 
carbonate,  1  part  of  ammonia  water,  and  3  parts  of  water),  shake  for  five  minutes, 
and  filter.  The  filtrate  acidulated  with  nitric  acid  may  exhibit  at  most  a  faint 
turbidity.  (Indicating  less  than  0.06  per  cent  HC1.) 

Hydriodic  Acid.  —  On  adding  1  drop  of  ferric  chloride  solution  to  5  c.c.  of 
hydrobromic  acid,  and  shaking  with  5  c.c.  of  chloroform,  the  latter  should 
not  acquire  a  violet  color.  (Indicating  less  than  0.0156  per  cent  HI.) 

Phosphorous  and  Phosphoric  Acids.  —  Heat  1  c.c.  of  hydrobromic  acid  with 
1  c.c.  of  nitric  acid  to  boiling,  allow  to  cool,  and  then  add  4  c.c.  of  ammonia 
water  followed  by  5  c.c.  of  magnesia  mixture.*  No  precipitate  should  form  on 
standing  fifteen  hours.  (Indicating  less  than  0.0075  per  cent  PzOs.) 

Calcium.  —  To  10  c.c.  of  hydrobromic  acid  diluted  with  10  c.c.  of  water 
and  mixed  with  15  c.c.  of  ammonia  water,  ammonium  oxalate  solution  is  added. 
No  precipitate  should  form  on  standing  two  hours.  (Indicating  less  than  0.005 
per  cent  Ca.) 

Quantitative  Determination.  —  Dilute  5  gm.  of  hydrobromic  acid  with  50 
c.c.  of  water,  and  titrate  with  normal  potassium  hydroxide  solution,  using  methyl 
orange  as  indicator.  At  least  24.6  c.c.  of  the  normal  alkali  solution  should  be 
required  to  effect  the  change  in  color. 

1  c.c.  of  normal  KOH  =  0.08093  gm,  of  HBr,  log.  90806. 


ACID    HYDROCHLORIC 

HC1.     Mol.  Wt.  36.47 

I 

ACID  HYDROCHLORIC,  Sp.Gr.   1.19 
(Fuming  Hydrochloric  Acid) 

A  clear,  colorless  liquid,  fuming  in  the  air,  and  of  specific  gravity 
1.19.     The  liquid  contains  about  37  per  cent  of  HC1. 

TESTS   OF  PURITY 

Sulphuric  Acid.  —  Evaporate  85  c.c.  of  hydrochloric  acid  in  a  platinum  dish 
to  about  5  c.c.,  dilute  the  residue  with  20  c.c.  of  water,  and  add  barium  chloride 


*  Dissolve  110  gm.  crystallized  magnesium  chloride  and  140  gm.  ammonium 
chloride  in  1300  gm.  of  water,  then  add  700  gm.  ammonia  water. 


10    /  CHEMICAL  REAGENTS 


solution.  No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen 
hours.  (Indicating  less  than  0.000125  per  cent  SO3.) 

Non-volatile  Matter.  —  85  c.c.  of  hydrochloric  acid,  when  evaporated  in  a 
platinum  dish  on  the  water-bath,  and  subsequently  ignited,  must  leave  no 
weighable  residue.  (Indicating  less  than  0.0005  per  cent.) 

Chlorine.  —  Dilute  10  c.c.  of  hydrochloric  acid  with  50  c.c.  of  water  and  add 
zinc  iodide-starch  solution.  The  liquid  must  not  develop  a  blue  color  within 
ten  minutes.  (Indicating  less  than  0.00016  per  cent  Cl.) 

Sulphurous  Acid.  —  50  c.c.  of  water  are  colored  blue  by  the  addition  of  1 
drop  of  decinormal  iodine  solution  and  a  few  drops  of  starch  solution.  Then 
add  a  mixture  containing  5  c.c.  of  the  hydrochloric  acid  to  be  tested  and  50  c.c. 
of  water.  The  liquid  must  not  be  decolorized  after  being  shaken.  (Indicating 
less  than  0.005  per  cent  as  SO2.) 

Heavy  Metals.  —  (a)  Dilute  20  c.c.  of  hydrochloric  acid  with  200  c.c.  of 
water,  warm  the  liquid  to  about  70°  C.,  and  pass  into  it  hydrogen  sulphide  gas. 
No  change  should  be  apparent.  (Indicating  none  present.) 

(6)  Evaporate  60  c.c.  of  the  acid  to  about  10  c.c.,  dilute  with  water  to  40 
c.c.,  add  50  c.c.  ammonia  water  and  a  few  drops  of  ammonium  sulphide  solution. 
No  green  or  dark  color  should  develop,  nor  should  a  precipitate  form.  (Indi- 
cating none  present.) 

(c)  A  reddish  color  should  not  develop  on  adding  potassium  sulphocyanate 
solution  to  6  c.c.  of  the  acid  diluted  with  water  to  20  c.c.  (Indicating  less  than 
0.0001  per  cent  Fe.) 

Calcium.  —  On  diluting  20  c.c.  of  hydrochloric  acid  with  20  c.c.  of  water  and 
adding  50  c.c.  of  ammonia  water,  followed  by  a  few  c.c.  of  ammonium  oxalate 
solution,  no  precipitate  should  form  on  standing  two  hours.  (Indicating  less 
than  0.001  per  cent  Ca.) 

Arsenic.  —  100  c.c.  hydrochloric  acid  are  added  by  drops  to  30  c.c.  of  nitric 
acid  (sp.gr.  1.3)  heated  to  about  60°  C.  After  the  addition  of  5  c.c.  of  arsenic-free 
sulphuric  acid  (sp.gr.  1.84)  to  the  mixture  it  is  evaporated  as  far  as  possible  on 
a  water-bath,  and  then  heated  on  a  sand-bath  until  it  gives  off  fumes  of  sulphuric 
trioxide.  A  Marsh  apparatus  is  started,  using  20  gm.  of  arsenic-free,  granulated 
zinc  and  dilute  (1  :  5)  sulphuric  acid;  then  the  residue  from  the  above  evaporation 
is  washed  into  the  generating  flask  of  the  apparatus,  diluted  with  20  c.c.  of  water. 
After  the  apparatus  has  been  in  action  for  one  hour,  there  may  be  at  most  a  very 
slight  deposit  in  the  reduction  tube,  but  no  distinctly  visible  arsenic  mirror. 
(Indicating  not  more  than  0.00001  per  cent  As.) 

Quantitative  Determination.  —  The  strength  of  the  acid  may  be  most  simply 
ascertained  from  the  specific  gravity.*  On  diluting  3  gm.  of  hydrochloric  acid 
with  50  c.c.  of  water,  and  titrating  with  normal  potassium  hydroxide  solution, 
using  methyl  orange  as  indicator,  not  less  than  30.5  c.c.  of  the  normal  alkali 
should  be  required  to  effect  the  color  change. 

1  c.c.  of  normal  KOH  =  0.03647  gm.  of  HC1,  log.  56194. 


*See  the  table  by  Lunge  and  Marchlewski,  in  Lunge's  Chem.-Tech.  Unter- 
such.-Meth.,  5  ed.,  I,  419  (1904);  U.  S.  Pharmacopoeia,  VIII,  p.  612  (1905). 
Compare  J.  Soc.  Chem.,  Ind.,  24,  789  (1905);  also  Landolt-Bornstein-Roth, 
Physikalish-Chemische  Tabellen,  4  ed.,  262  (1912). 


ACID  HYDROFLUORIC  11 

ACID  HYDROCHLORIC,   Sp.Gr.   1.126 

II 
(Diluted  Hydrochloric  Acid) 

A  clear,  colorless  liquid,  of  specific  gravity  1.126,  and  containing 
about  25  per  cent  of  HC1. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Fuming  Hydrochloric  Acid.  But, 
for  every  10  gm.  (or  c.c.)  of  fuming  acid,  use  15  gm.  (or  c.c.)  of  the  acid  of  sp.gr. 
1.126. 

Quantitative  Determination.*  —  Dilute  5  gm.  of  the  acid  with  50  c.c.  of  water, 
and  titrate  with  normal  potassium  hydroxide  solution,  using  methyl  orange  as 
indicator.  At  least  34.3  c.c.  of  the  normal  alkali  should  be  required  for  neu- 
tralization. 


ACID   HYDROFLUORIC 

HF.     Mol.  Wt.  20.01 

A  colorless,  or  almost  colorless,  liquid,  containing  about  48  per 
cent  of  HF.  It  fumes  in  the  air. 

TESTS   OF  PURITY 

In  these  tests  use  platinum  containers  as  much  as  possible. 

Non-volatile  Matter.  —  20  gm.  of  hydrofluoric  acid  evaporated  in  a  platinum 
dish,  and  gently  ignited,  should  leave  a  residue  weighing  not  more  than  0.001 
gm.  (Indicating  not  more  than  0.005  per  cent.) 

Sulphuric  Acid.  —  Evaporate  2  gm.  of  hydrofluoric  acid  in  a  platinum  dish 
on  the  water-bath,  take  up  the  residue  with  10  c.c.  of  water,  and  to  this  solution 
add  a  few  drops  of  nitric  acid  and  some  barium  nitrate  solution.  An  immediate 
turbidity  must  not  occur;  and  even  after  some  time  the  liquid  should  exhibit, 
at  most,  a  slight  opalescence.  (Indicating  less  than  0.005  per  cent  SO3.) 

Calcium.  —  Dilute  5  gm.  of  hydrofluoric  acid  with  50  c.c.  of  water  and  add 
ammonia  water  in  excess,  followed  by  ammonium  oxalate  solution.  An  immediate 
turbidity  should  not  occur.  (Indicating  less  than  0.005  per  cent  Ca.) 

Magnesium.  —  Dilute  5  gm.  of  hydrofluoric  acid  with  50  c.c.  of  water,  and 
add  ammonia  water  until  the  liquid  has  an  alkaline  reaction;  on  now  adding 
ammonium  phosphate  solution,  no  precipitate  should  form  on  standing  three 
hours.  (Indicating  less  than  0.001  per  cent  Mg.) 


12  CHEMICAL  REAGENTS 


Heavy  Metals.  —  (a)  Dilute  10  gm.  of  hydrofluoric  acid  with  40  c.c.  of  water, 
warm  the  liquid  to  about  70°  C.  and  pass  through  it  hydrogen  sulphide  gas. 
Neither  a  yellow  nor  a  dark-colored  precipitate  should  form.  (Indicating  none 
present.) 

(6)  Dilute  5  gm.  of  hydrofluoric  acid  with  50  c.c.  of  water,  make  the  solution 
alkaline  with  ammonia  water,  and  add  ammonium  sulphide  solution.  A  green 
coloration  must  not  develop,  nor  should  a  precipitate  form.  (Indicating  none 
present.) 

Hydrochloric  Acid.  —  Dilute  2  gm.  of  hydrofluoric  acid  with  50  c.c.  of  water, 
and  add  a  few  drops  of  nitric  acid  and  silver  nitrate  solution.  The  liquid  may 
exhibit,  at  most,  a  faint  opalescence.  (Indicating  less  than  0.001  per  cent  Cl.) 

Hydrosilicofluoric  Acid.  —  On  diluting  5  gm.  of  hydrofluoric  acid  with  20 
c.c.  of  water  and  adding  2  c.c.  of  a  cold,  saturated  potassium  chloride  solution, 
the  further  addition  of  40  c.c.  of  alcohol  (of  about  85  per  cent  by  weight)  should 
cause  no  turbidity  or  precipitate.  (Indicating  less  than  0.3  per  cent  H2SiF6.) 

Sulphurous  Acid.  —  A  mixture  of  10  gm.  of  hydrofluoric  acid  and  40  c.c.  of 
water  should  show  a  blue  color  upon  the  addition  of  one  drop  of  decinormal 
iodine  solution  and  starch  solution.  (Indicating  less  than  0.003  per  cent  SO2.) 

Quantitative  Determination.  —  Dilute  2  gm.  of  hydrofluoric  acid  with  50 
c.e.  of  water  and  titrate  with  normal  potassium  hydroxide  solution,  using  phenol- 
phthalein  as  indicator. 

1  c.c.  of  normal  KOH=  0.02001  gm.  of  HF,  log.  30125. 

NOTE.  —  Regarding  the  titration  of  hydrofluoric  acid  in  the  presence  of 
hydrosilicofluoric  acid,  see  Katz,  Chem.  Ztg.,  28,  356,  387  (1904);  abst.,  J.  Chem. 
Soc.,  86,  II,  442  (1904). 


ACID  HYDROSILICOFLUORIC 

(Fluosilicic  or  Silicofluoric  Acid) 
H2SiF6.    Mol.  Wt.  144.32 

A  clear,  colorless  liquid  having  a  specific  gravity  of  about  1.06. 
This  specific  gravity  corresponds  to  a  content  of  about  8  per  cent 
H2SiF6. 

TESTS  OF  PURITY 

Non- volatile  Matter.  —  5  c.c.  of  hydrosilicofluoric  acid  evaporated  in  a 
platinum  dish  should  leave  no  weighable  residue.  (Indicating  less  than  0.01 
per  cent.) 

Heavy  Metals.  —  Dilute  5  c.c.  of  hydrosilicofluoric  acid  with  10  c.c.  of  water, 
add  a  few  drops  of  hydrochloric  acid  and  10  c.c.  of  hydrogen  sulphide  water. 
No  visible  change  should  take  place.  (Indicating  none  present.) 

Sulphuric  Acid.  —  On  diluting  5  c.c.  of  hydrosilicofluoric  acid  with  10  c.c. 
of  water  and  adding  2  c.c.  of  a  10  per  cent  solution'  of  barium-free  strontium 
nitrate,  no  precipitate  should  form,  even  on  standing  fifteen  hours.  (Indicating 
less  than  0.028  per  cent  S08.) 

Quantitative  Determination.  —  Titrate  10  gm.  of  the  hydrosilicofluoric  acid 
with  normal  sodium  hydroxide  solution,  using  methyl  orange  as  indicator.  Then 
add  to  the  above  solution  (neutral  to  methyl  orange)  50  c.c.  of  water,  heat  to 
boiling,  and  with  the  same  alkali  titrate  again,  using  phenolphthalein  as  indi- 


IODIC  ANHYDRIDE  13 


eator.  To  obtain  the  permanent  pink  color  should  require  exactly  twice  as 
much  alkali  as  was  required  to  make  the  solution  neutral  to  methyl  orange.  The 
amount  of  alkali  consumed  in  the  second  titration  is  used  to  calculate  the 
strength  of  the  acid. 

1  c.c.  normal  NaOH  =  0.03608  gm.  of  H2SiF6,  log.  55727. 

NOTE.  —  Regarding  the  determination  of  hydrosilicofluoric  acid,  see  Katz, 
Chem.  Ztg.,  28,  356,  387  (1904);  abst.,  J.  Chem.  Soc.,  86,  II,  442  (1904).  S. 
Kohn  and  L.  Wesseley,  Chem.  Ztg.,  31,  204,  1207  (1907);  abst.,  J.  Chem.  Soc., 
92,  II,  300  (1907). 


ACID  IODIC 
HIO3.    Mol.  Wt.  175.93 

Colorless,  rhombic  crystals,  or  white,  crystalline  powder,  easily 
soluble  (1  :  1)  in  water,  but  difficultly  soluble  in  alcohol.  The 
aqueous  solution  first  reddens  blue  litmus  paper  and  then  bleaches  it. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  On  heating  2  gm.  of  iodic  acid  no  weighable  residue 
should  remain.  (Indicating  less  than  0.025  per  cent.) 

Solubility.  —  1  gm.  of  iodic  acid  should  dissolve  completely  in  1  c.c.  of  water, 
and  yield  a  colorless  solution. 

Quantitative  Determination.  —  Dissolve  1  gm.  of  iodic  acid  in  water  and 
dilute  to  100  c.c.  Dilute  10  c.c.  of  this  solution  with  50  c.c.  of  water,  and  add 
2  gm.  of  potassium  iodide  and  5  c.c.  of  dilute  sulphuric  acid.  Titrate  the  liberated 
iodine  with  decinormal  sodium  thiosulphate  solution,  using  starch  solution  as 
indicator. 

1  c.c.  of  decinormal  Na2S2O3  =  0.002932  gm.  of  HI03,  log.  46716. 


(ACID)   IODIC  ANHYDRIDE 

(Iodine  Pentoxide) 
I2O5.    Mol.  Wt.  333.84 

A  white,  crystalline  powder,  soluble  in  water  with  the  formation 
of  the  hydrated  acid,HIOs,  but  insoluble  in  absolute  alcohol  and  ether. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Acid  Iodic,  and  the  conditions 
there  described  are  to  be  observed. 

1  c.c.  of  decinormal  Na2S2O3  =  0.002782  gm.  of  I205,  log.  44436. 


14  CHEMICAL  REAGENTS 


ACID   MOLYBDIC 

H2MoO4.    Mol.  Wt.  162.02 

A  white  or  slightly  yellowish  powder,  containing  about  85  per 

cent  of  MoOa. 

TESTS   OF  PURITY 

Solubility  in  Ammonia  Water;  Hea^y  Metals.  —  2  gm.  of  molybdic  acid 
should  completely  dissolve  in  15  c.c.  of  ammonia  water,  yielding  a  clear  solution. 
On  the  addition  of  hydrogen  sulphide  water  to  this  liquid  it  acquires  a  greenish- 
yellow  color;  a  brown  color  or  a  precipitate  should  not,  however,  develop. 
(Indicating  no  heavy  metals  present.) 

Phosphoric  Acid.  Quantitative  Determination.  —  As  detailed  under  (Acid) 
Molybdic  Anhydride,  below. 

(ACID)   MOLYBDIC  ANHYDRIDE 

(Molybdic  Acid,  100  per  cent) 
MoO3.    Mol.  Wt.  144.00 

A  slightly  yellowish  powder,  often  exhibiting  a  faintly  bluish 
tint,  due  to  the  presence  of  other  oxides  of  molybdenum.  The 
preparation  contains  about  100  per  cent  of  MoOs,  and  is  free  from 
ammonia  and  nitric  acid. 

TESTS   OF  PURITY 

Alkalies.  —  On  heating  1  gm.  of  molybdic  anhydride  in  a  test-tube,  the  par- 
ticles in  contact  with  the  heated  wall  of  the  tube  begin  to  melt  at  a  red  heat, 
while  upon  the  cooler  upper  surface  a  crystalline  formation  of  sublimed  anhydride 
may  be  observed.  The  whole  should  not  fuse  to  a  dark-colored  mass  at  a 
lower  temperature.  (Indicating  no  alkalies  present.) 

Ammonium  Salts.  —  On  boiling  1  gm.  of  molybdic  anhydride  with  sodium 
hydroxide  solution,  there  must  be  no  liberation  of  ammonia  (to  be  ascertained 
by  means  of  moistened  litmus  paper).  (Indicating  less  than  0.0035  per  cent  NH3.) 

Solubility  in  Ammonia  Water;  Heavy  Metals. — 5  gm.  of  molybdic  anhydride, 
when  gently  heated  with  40  c.c.  of  ammonia  water,  should  entirely  dissolve, 
yielding  a  clear  solution.  The  solution  acquires  a  slight  yellow  color  on  adding 
hydrogen  sulphide  water.  This  color  must  not  change  within  ten  minutes,  nor 
should  a  precipitate  form.  (Indicating  no  heavy  metals  present.) 

Phosphoric  Acid.  —  Dissolve  10  gm.  of  molybdic  anhydride  in  25  c.c.  of 
ammonia  water.  The  solution  is  poured  into  150  c.c.  of  nitric  acid  and  allowed 
to  stand  for  fifteen  hours  at  a  temperature  of  about  40°  C.  A  yellow  precipitate 
must  not  appear.  (Indicating  less  than  0.0005  per  cent  P2O5.) 

Nitric  Acid.  —  Shake  1  gm.  of  molybdic  anhydride  with  10  c.c.  of  water, 
and  add  a  small  crystal  of  sodium  chloride,  followed  by  one  drop  of  a  1  :  1000 
solution  of  indigo;  the  blue  color  of  the  solution  must  not  disappear  on  adding 
10  c.c.  of  concentrated  sulphuric  acid  and  stirring.  (Indicating  less  than  0.0032 
per  cent  N2O5.) 


ACID  NITRIC  15 


Sulphates  and  Chlorides.  —  Dissolve  10  gm.  of  molybdic  anhydride  in  25 
c.c.  of  ammonia  water,  pour  the  solution  into  150  c.c.  of  nitric  acid,  and  add 
barium  nitrate  and  silver  nitrate  solutions.  No  turbidity  should  be  produced. 
(Indicating  less  than  1.0  per  cent  SO3,  and  less  than  0.002  per  cent  Cl.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  molybdic  anhydride  in  a 
mixture  of  50  c.c.  of  water  and  3  c.c.  of  ammonia  water,  with  the  aid  of  a  gentle 
heat.  Acidulate  the  solution  with  5  c.c.  of  acetic  acid  (sp.gr.  1.040-1.042),  dilute 
with  200  c.c.  of  water,  heat  to  boiling,  then  add  a  solution  of  1.5  gm.  crystallized 
lead  acetate  in  20  c.c.  of  water.  Boil  for  several  minutes  with  constant  stirring, 
whereby  the  precipitate,  at  first  milky,  is  rendered  granular  and  easy  to  filter. 
Collect  the  precipitate  on  a  filter  previously  dried  at  100°  C.  and  weighed,  and 
wash  it  with  boiling  water  until  the  washings  cease  to  afford  a  reaction  with 
hydrogen  sulphide  water.  Dry  the  precipitate  to  constant  weight  at  100°  C. 
and  then  ignite  a  portion  of  it.  The  ignited  residue  has  the  composition  PbMoC>4. 

PbMo04X0.39247=Mo03,  log.  59380. 


ACID   NAPHTHYLAMINESULPHONIC 

(Alphanaphthylaminesulphonic  Acid  ;  Naphthionic  Acid) 
2C10H6NH2S03H  i  :  4+H2O.    Mol.  Wt.  464.32 

A  white  powder,  or  small,  lustrous,  colorless  needles  (when 
crystallized  from  hot  water),  which  carbonize  but  do  not  melt  on 
being  heated.  Naphthylaminesulphonic  acid  is  soluble  in  about 
4000  parts  of  cold  water,  more  readily  in  hot  water,  scarcely  soluble 
in  alcohol,  and  almost  insoluble  in  ether.  The  solution  in  ammonia 
water  exhibits  a  violet  fluorescence. 

NOTE.  —  Regarding  the  use  of  naphthylaminesulphpnic  acid  for  the  detection 
and  colorimetric  determination  of  small  quantities  of  nitrous  acid,  see  E.  Riegler, 
Z.  anal.  Chem.,  35,  677  (1896):  absi.,  J.  Chem.  Soc.,  72,  II,  230  (1897);  Z.  anal. 
Chem.,  36,  306  (1897);  abst.,  J.  Chem.  Soc.,  72,  II,  385  (1897). 


ACID   NITRIC 
HNO3.     Mol.  Wt.  63.02 

I 
ACID   NITRIC,  Sp.Gr.   1.40-1.42* 

A  clear,  colorless,  or  yellowish  liquid,  specific  gravity  1.40  to 
1.42,  containing  about  65  to  69  per  cent  by  weight  of 


*  See  the  tables  of  specific  gravity  and  per  cent  in  Lunge's  Chem. -Tech. 
Untersuch.-Meth.,  5  ed.,  I,  326  (1904);  U.  S.  Pharmacopoeia,  VIII,  p.  613  (1905); 
Landolt-Bornstein-Roth,  Physikalisch-Chemische  Tabellen,  4  ed.,  263  (1912). 
Compare  J.  Soc.  Chem.,  Ind.,  24,  788  (1905). 


16  CHEMICAL  REAGENTS 


TESTS  OF  PURITY 

Non-volatile  Matter.  —  75  c.c.  of  nitric  acid  on  evaporation  should  leave  no 
weighable  residue.  (Indicating  less  than  0.00047  per  cent.) 

Sulphuric  Acid.  —  Add  to  25  c.c.  of  nitric  acid  a  small  amount  of  sodium  car- 
bonate, evaporate  the  solution  to  dryness,  take  up  the  residue  with  50  c.c.  of 
water,  and  add  barium  chloride  solution.  No  weighable  precipitate  of  barium 
sulphate  should  form  on  standing  fifteen  hours.  (Indicating  less  than  0.00005  per 
cent  SO3.) 

Hydrogen-Halogen  Acids.  —  50  c.c.  of  nitric  acid  diluted  with  50  c.c.  of  water 
must  not  appear  changed  on-the  addition  of  silver  nitrate  solution.  (Indicating 
less  than  0.000015  per  cent  Cl.) 

Heavy  Metals.  —  Add  to  25  c.c.  of  the  acid  a  slight  excess  of  ammonia  water, 
and  dilute  to  about  100  c.c.  On  adding  a  few  drops  of  ammonium  sulphide 
solution  no  green  or  dark  color  should  develop,  nor  should  a  precipitate  form. 
(Indicating  none  present.) 

lodic  Acid  and  Iodine.  —  On  diluting  20  c.c.  of  nitric  acid  with  20  c.c.  of  water, 
adding  a  small  piece  of  metallic  zinc,  and  shaking  with  a  small  quantity  of  chloro- 
form, the  chloroform  should  not  be  colored  violet.  (Indicating  less  than  0.0005 
per  cent  as  I.) 

Earths.  —  Dilute  10  c.c.  of  nitric  acid  with  80  c.c.  of  water  and  render  slightly 
alkaline  with  ammonia  water.  On  adding  ammonium  oxalate  solution  no  tur- 
bidity should  result.  (Indicating  less  than  0.0002  per  cent  earths  as  Ca.) 

Arsenic.  —  50  c.c.  of  nitric  acid  are  mixed  with  5  c.c.  of  arsenic-free  sulphuric 
acid  (sp.gr.  1.84)  and  evaporated  as  far  as  possible  on  a  water-bath,  and  then 
heated  on  a  sand-bath  until  fumes  of  sulphur  trioxide  are  given  off.  A  Marsh 
apparatus  is  started,  using  20  gm.  of  arsenic-free,  granulated  zinc  and  dilute 
(1  :  5)  sulphuric  acid;  then  the  residue  from  the  above  evaporation,  diluted 
with  20  c.c.  of  water,  is  washed  into  the  generating  flask  of  the  apparatus.  After 
the  apparatus  has  been  in  action  for  one  hour  no  mirror  of  arsenic  should  be 
visible.  (Indicating  less  than  0.0000075  per  cent  As.) 

Quantitative  Determination.  —  Dilute  2  gm.  of  nitric  acid  with  50  c.c.  of 
water  and  titrate  with  normal  potassium  hydroxide  solution,  using  methyl  orange 
as  indicator. 

1  c.c.  of  normal  KOH  =  0.06302  gm.  of  HNO3,  log.  79948. 


II 
ACID  NITRIC,  Sp.Gr.  1.30 

A  clear,  colorless  liquid,  of  specific  gravity  1.30,  and  containing 
about  47  per  cent  of  HNOa. 

TESTS  OF  PURITY 

The  tests  to  be  made  are  those  given  under  Acid  Nitric,  Sp.Gr.  1.40-1.42, 
observing  the  conditions  there  described.  But  instead  of  1  c.c.  of  the  acid  sp  gr 
1.40-1.42,  use  1.5  c.c.  of  the  acid  sp.gr.  1.30. 


ACID  NITRIC  17 

III 
ACID  NITRIC,  Sp.Gr.   1.20 

A  clear,  colorless  liquid  of  specific  gravity  1.20,  and  containing 
about  33  per  cent  of  HN03. 

TESTS  OF  PURITY 

The  tests  to  be  made  those  given  under  Acid  Nitric,  Sp.Gr.  1.40-1.42,  observ- 
ing the  conditions  there  described.  But,  instead  of  1  c.c.  of  acid,  sp.gr.  1.40- 
1.42,  use  2  c.c.  of  acid  sp.gr.  1.20. 

IV 
ACID  NITRIC,  Sp.Gr.   1.150-1.152 

A  clear,  colorless  liquid,  of  specific  gravity  1.150-1.152  containing 
about  25  per  cent  of  HNOs. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Acid  Nitric,  Sp.Gr.  1.40-1.42, 
observing  the  conditions  there  described.  But,  instead  of  1  c.c.  of  acid,  sp.gr. 
1.40-1.42,  use  2.5  c.c.  of  acid  sp.gr.  1.150-1.152. 

ACID  NITRIC,  CRUDE,  Sp.Gr.   1.38-1.40 

A  clear,  colorless,  or  yellowish  liquid  of  specific  gravity  1.38-1.40, 
and  containing  61  to  65  per  cent  of  HNOs. 

TEST   OF  PURITY 

Non-volatile  Matter.  —  5  c.c.  of  crude  nitric  acid  on  evaporation  should  leave 
no  weighable  residue.  (Indicating  less  than  0.007  per  cent.) 

ACID  NITRIC,  FUMING,   Sp.Gr.   1.486-1.500* 

A  colorless  or  slightly  yellowish  liquid  of  specific  gravity  1.486- 
1.500,  and  containing  87.7  to  94  per  cent  of  nitric  acid,  HNOs. 
Exposed  to  light  it  soon  becomes  brown,  and  then  gives  off  suffocating 
yellowish-red  vapors. 

TESTS   OF  PURITY 

The  tests  of  purity  to  be  made  are  those  given  under  Acid  Nitric,  Sp.Gr.  1.40- 
1.42.  But  for  5  c.c.  of  acid  sp.gr.  1.40-1.42  use  3  c.c.  of  fuming  nitric  acid. 

*  See  foot-note  under  Acid  Nitric,  Sp.Gr.  1.40-1.42. 


18  CHEMICAL  REAGENTS 

ACID   OXALIC,  CRYSTALS 
H2C2O4+2H2O.    Mol.  Wt.  126.05 

Colorless,  odorless,  prismatic  crystals,  solulle  in  10  parts  of  cold 
water,  in  about  3  parts  of  boiling  water,  and  in  2.5  parts  of  alcohol; 
difficultly  soluble  in  ether.  On  heating  the  hydrated  oxalic  acid 
in  a  capillary  tube,  it  liquefies  at  98°  C.  in  its  water  of  crystal- 
lization. On  being  heated  to  70°  C.,  the  hydrated  acid  is  rendered 
anhydrous,  sublimes  at  about  100°  C.,  and  melts  at  187°  C.  The 
crystals  must  contain  99.8-100  per  cent  of  the  hydrated  acid, 
H2C2O4+2H20,  and  must  not  appear  effloresced. 

TESTS   OF  PURITY 

Ash.  —  3  gm.  of  oxalic  acid  upon  ignition  in  a  platinum  crucible  should 
leave  no  weighable  residue.  (Indicating  less  than  0.017  per  cent.) 

Sulphuric  Acid.  —  Dissolve  5  gm.  of  oxalic  acid  in  100  c.c.  of  water,  and 
add  1  c.c.  of  hydrochloric  acid  and,  1  c.c.  barium  chloride  solution.  No  precip- 
itate of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating 
less  than  0.004  per  cent  SO3.) 

Chlorides.  —  Dissolve  5  gm.  of  oxalic  acid  in  50  c.c.  of  water,  add  15  c.c. 
of  nitric  acid  and  a  few  drops  of  silver  nitrate  solution.  The  solution  may 
exhibit  at  most  a  slight  opalescent  turbidity.-  (Indicating  less  than  0.0004 
per  cent  Cl.) 

Heavy  Metals.  —  The  1  :  10  aqueous  solution  must  be  perfectly  clear,  and 
on  adding  hydrogen  sulphide  water  to  30  c.c.  of  it,  no  change  should  be  observed. 
On  now  adding  ammonia  water  to  this  liquid  until  alkaline,  neither  a  green  nor 
a  brown  coloration  should  develop,  nor  should  a  precipitate  form.  (Indicating 
none  present.) 

Ammonium  Compounds.  —  On  dissolving  2.5  gm.  of  oxalic  acid  and  5  gm. 
of  potassium  hydroxide  (purest)  in  30  c.c.  of  water,  and  adding  to  the  solution 
about  15  drops  of  Nessler's  solution,  at  most  a  slight  yellow  color  should  develop, 
but  never  a  brownish-red  one.  (Indicating  less  than  0.002  per  cent  NH3.) 

Nitric  Acid.  —  On  overlaying  10  c.c.  of  a  solution  of  diphenylamine*  in  con- 
centrated sulphuric  acid  with  10  c.c.  of  a  1  :  10  aqueous  solution  of  oxalic  acid, 
a  blue  zone  should  not  form  at  the  contact-surfaces  of  the  two  liquids.  (Indi- 
cating less  than  0.007  per  cent  N2O5.) 

Quantitative  Determinations.  —  (a)  Acidimetrically :  Dissolve  1  gm.  of  crys- 
tallized oxalic  acid  in  water,  dilute  to  100  c.c.,  and  titrate  25  c.c.  of  the  solution 
with  one-fifth  normal  potassium  hydroxide  solution,  using  phenolphthalein  as 
indicator.  Perform  the  titration  at  60°  C. 

1  c.c.  of  one-fifth  normal  KOH  =  0.012605  gm.  of  H2C2O4+2H2O,  log.  10054. 

(6)  By  Oxidimetry:  To  25  c.c.  of  the  aqueous  solution  (1  gm.  of  crystallized 
oxalic  acid  in  water  as  above)  add  6  to  8  c.c.  of  concentrated  sulphuric  acid, 
heat  to  about  60°  C.,  and  titrate  with  decinormal  potassium  permanganate 
solution. 

1  c.c.  of  decinormal  KMnO4  =  0.0063025  gm.  of  H2C2O4  +2H20,  log.  79950. 

*  See  footnote  under  Diphenylamine. 


ACID  PERCHLORIC  19 

ACID   PERCHLORIC 
HC1O4.     Mol.  Wt.  100.47 

A  colorless  liquid  of  specific  gravity  1.12,  and  containing  about 
20  per  cent  of  HC104. 

TESTS  OF  PURITY       . 

Non-volatile  Matter.  — 10  gm.  of  perchloric  acid  when  evaporated  and 
ignited  should  leave  no  weighable  residue.  (Indicating  less  than  0.005  per  cent.) 

Sulphuric  Acid.  —  On  diluting  5  c.c.  of  perchloric  acid  with  100  c.c.  of  water, 
and  adding  5  c.c.  of  hydiochloric  acid,  followed  by  barium  chloride  solution,  a 
precipitate  of  barium  sulphate  should  not  form  on  standing  fifteen  hours.  (Indi- 
cating less  than  0.005  per  cent  SO3.) 

Hydrochloric  Acid.  —  The  mixture  obtained  by  diluting  5  c.c.  of  perchloric 
acid  with  25  c.c.  of  water  and  adding  3  c.c.  of  nitric  acid  should  not  be  rendered 
more  than  slightly  turbid  by  silver  nitrate  solution.  (Indicating  less  than 
0.0005  per  cent  Cl.) 

Barium.  —  10  c.c.  of  perchloric  acid  diluted  with  50  c.c.  of  water  must  not 
become  turbid  within  five  minutes  on  adding  dilute  sulphuric  acid.  (Indicating 
less  than  0.0025  per  cent  Ba.) 

Heavy  Metals.  —  10  c.c.  of  perchloric  acid  diluted  with  40  c.c.  of  water 
must  show  no  change  on  adding  hydrogen  sulphide  water;  and  on  adding  to 
this  solution  10  c.c.  of  ammonia  water  and  a  few  drops  of  ammonium  sulphide 
solution,  a  precipitate  should  not  form,  nor  should  the  liquid  acquire  a  brown 
color.  (Indicating  none  present.) 


ACID   PHOSPHOMOLYBDIC 

2oMoO3-2H3PO4+48H2O.     Mol.  Wt.  3940.89 

Yellow,  lustrous  crystals,  easily  and  completely  soluble  in  water, 
and  yielding  with  the  latter  an  acid  solution. 

TESTS   OF  PURITY 

Solubility,  Heavy  Metals,  and  Earths.  —  1  gm.  of  phosphomolybdic  acid 
should  completely  dissolve  in  10  c.c.  of  water  upon  gentle  warming.  On  adding 
to  this  solution  two  or  three  drops  of  ammonia  water,  a  yellow  precipitate  forms, 
which  completely  redissolves  on  the  addition  of  5  c.c.  of  the  ammonia  water. 
On  now  adding  to  this  solution  ammonium  sulphide  solution,  a  precipitate  should 
not  form.  At  most  a  slight  green  color  may  appear.  (Indicating  at  most  a 
trace  of  heavy  metals.)  The  addition  of  ammonium  oxalate  solution  to  this 
latter  mixture  should  cause  no  visible  change.  (Indicating  less  than  0.02  per 
cent  earths  as  Ca.) 


20  CHEMICAL  REAGENTS. 

ACID    PHOSPHORIC,    ORTHO- 

H3PO4.    Mol.  Wt.  98.06 

I 
ACID  PHOSPHORIC,  Sp.Gr.  1.70. 

A  clear,  colorless,   odorless,  syrupy  liquid,  of  specific  gravity 
1.70,  and  containing  about  83  per  cent  of  H3P04. 
TESTS   OF  PURITY 

Volatile  Acids.  —  Mix  30  c.c.  of  the  phosphoric  acid  with  50  c.c.  of  water 
in  a  distilling  flask.  Distil*  off  50  c.c.,  and  titrate  the  distillate  with  decinormal 
potassium  hydroxide  solution,  using  methyl  orange  as  indicator.  Not  more 
than  0.1  c.c.  of  the  decinormal  alkali  solution  should  be  required.  (Indicating 
less  than  0.00125  per  cent  as  HNO3.) 

Nitric  Acid.  —  2  c.c.  of  phosphoric  acid  mixed  with  2  c.c.  of  concentrated 
sulphuric  acid,  and  overlaid  with  1  c.c.  of  a  solution  of  ferrous  sulphate,  must 
not  develop  a  colored  zone.  (Indicating  less  than  0.0048  per  cent  N2OP.) 

Hydrogen-Halogen  Acids  and  Phosphorous  Acid.  —  2  c.c.  of  phosphoric  acid 
diluted  with  18  c.c.  of  water  should  give  no  reaction  with  silver  nitrate  solution 
either  in  the  cold  or  on  boiling.  (Indicating  less  than  0.0003  per  cent  hydrogen- 
halogen  acids  as  Cl,  and  less  than  0.095  per  cent  P2O3.) 

Sulphuric  Acid.  —  On  adding  barium  chloride  solution  to  20  c.c.  of  the 
diluted  acid  (1  :  10),  no  precipitate  of  barium  sulphate  should  form  on  standing 
two  or  three  hours.  (Indicating  less  than  0.0025  per  cent  SO3.) 

Metaphosphoric  Acid.  —  On  dropping  the  acid  diluted  with  10  volumes  of 
water  into  a  dilute  solution  of  albumen,  no  turbidity  should  ensue.  (Indicating 
none  present.) 

Heavy  Metals,  Earths,  etc.  —  (a)  Dilute  the  acid  with  10  volumes  of  water, 
and  to  20  c.c.  of  the  mixture  add  hydrogen  sulphide  water.  There  should  be 
no  visible  change.  (Indicating  no  heavy  metals  present.) 

(6)  On  adding  10  c.c.  of  ammonia  water  to  20  c.c.  of  the  above  diluted  acid, 
no  precipitate  should  form  on  the  further  addition  of  either  ammonium  oxalate 
solution  (indicating  less  than  0.006  per  cent  earths  as  Ca),  or  ammonium  sulphide 
solution.  (Indicating  no  heavy  metals  present.) 

(c)  A  mixture  of  5  c.c.  of  phosphoric  acid  with  20  c.c.  of  absolute  alcohol 
should  remain  perfectly  clear.  (Indicating  no  earths,  etc.  present.) 

Substances  Oxidizable  by  Permanganate.  —  On  adding  5  drops  of  decinormal 
potassium  permanganate  solution  to  a  mixture  of  5  c.c.  of  phosphoric  acid  and 
5  c.c.  of  diluted  sulphuric  acid,  and  then  heating  for  5  minutes  at  100°  C.,  the 
red  color  of  the  liquid  should  not  disappear.  (Indicating  none  present.) 

Arsenic.  —  A  Marsh  apparatus  is  started,  using  20  gm.  of  arsenic-free,  gran- 
ulated zinc,  and  diluted  (1  :  5)  sulphuric  acid.  A  mixture  of  3  c.c.  of  phosphoric 
acid  with  20  c.c.  of  water  is  then  introduced  in  small  quantities  at  a  time,  the 
evolution  of  hydrogen  being  maintained  for  one  hour.  A  deposit  of  arsenic 
should  not  be  visible  in  the  reduction  tube  within  this  time.  (Indicating  less 
than  0.0002  per  cent  As.) 


*  In  order  to  prevent  spirting  over  of  phosphoric  acid,  the  flask  should  be 
provided  with  a  Kjeldahl  connecting  bulb  tube.  The  distillate  must  be  tested 
with  ammonium  molybdate  solution  for  phosphoric  acid. 


ACID  PHOSPHORIC  21 

Quantitative  Determination.  —  Dilute  1  gm.  of  phosphoric  acid  with  30  c.c. 
of  water,  and  titrate  with  normal  potassium  hydroxide,  using  phenolphthalein 
as  indicator.*  At  least  17  c.c.  of  normal  alkali  must  be  added  to  produce  the 
red  color. 

1  c.c.  of  normal  KOH  =  0.049032  gm.  of  H3PO4,  log.  69048. 

II 
ACID    PHOSPHORIC,    Sp.Gr.  1.12 

A  clear,  colorless,  odorless  liquid  of  specific  gravity  1.12,  and 
containing  about  20  per  cent  of  HsPO/i. 

TESTS  OF  PURITY 

The  tests  to  be  made  and  the  conditions  to  be  observed  are  those  given 
under  Acid  Phosphoric,  Sp.Gr.  1.70.  But  for  1  c.c.  of  the  phosphoric  acid  sp.gr. 
1.70,  use  4  c.c.  of  the  phosphoric  acid  sp.gr.  1.12. 

(ACID)   PHOSPHORIC  ANHYDRIDE 

(Phosphorus  Pentoxide) 
P2O6.    Mol.  Wt.  142.08 

A  white,  amorphous,  odorless,  bulky  powder,  which  dissolves 
in  water  with  a  hissing  noise,  forming  metaphosphoric  acid.  Phos- 
phoric anhydride  completely  sublimes  on  being  heated. 

TEST  OF  PURITY 

Arsenous  Acid.  —  Introduce  1  gm.  of  phosphoric  anhydride,  in  small  por- 
tions at  a  time,  into  20  c.c.  of  water,  and  while  warming  the  solution,  pass  into 
it  a  current  of  hydrogen  sulphide  gas.  The  liquid  may  acquire  at  most. a  slightly 
yellow  color,  but  a  yellow  precipitate  should  not  form.  (Indicating  less  than 
0.01  per  cent  As2O3.) 

ACID  PHOSPHOTUNGSTIC 
(P2O5-2oWO3-iiH2O)  +  i6H2O.     Mol.  Wt.  5268.51 

Small,  white,  or  slightly  yellowish-green  crystals,  easily  soluble 
in  water,  and  free  from  ammonia  and  nitric  acid. 

TESTS   OF  PURITY 

Nitrates.  —  Dissolve  1  gm.  of  phosphotungstic  acid  in  10  c.c.  of  water,  add 
a  granule  of  sodium  chloride  and  1  drop  of  indigo  solution  (1  :  1000),  followed 


*  Methyl  orange  may  be  used  instead  of  phenolphthalein.  In  this  case, 
however,  1  c.c.  of  the  normal  KOH= 0.09806  gm.  of  H3PO4,  log.  99149.  When 
titrating  with  phenolphthalein,  twice  as  many  cubic  centimeters  of  the  alkali 
solution  are  required  as  when  using  methyl  orange. 


22  CHEMICAL  REAGENTS 


by  10  c.c.  of  concentrated  sulphuric  acid.  The  blue  color  of  the  mixture  must 
not  disappear  within  10  minutes.  (Indicating  less  than  0.0032  per  cent  N2O5.) 

Ammonium  Salts.  —  On  heating  a  solution  of  1  gm.  of  phosphotungstic  acid 
in  10  c.c.  of  water,  with  5  c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3),  no 
ammonia  should  be  evolved  (to  be  ascertained  by  means  of  moistened  litmus 
paper).  (Indicating  less  than  0.0045  per  cent  NH3.) 

NOTE. — Regarding  a  method  for  the  quantitative  analysis  of  phosphotungstic 
acid,  see  F.  Kehrmann,  Ber.,  20,  1813  (1887);  abst.,  J.  Chem.  Soc.,  52,  777  (1887). 


ACID  PICRIC 

(Picronitric  Acid;  Trinitrophenol) 

C6H2(OH)(N02)3.    Mol.  Wt.  229.05 

Pale  yellow,  glistening  crystals,  melting  at  122.5°  C.,  soluble 
in  100  parts  of  cold  water  and  in  about  30  parts  of  boiling  water. 
The  acid  is  soluble  in  15  parts  of  alcohol,  in  75  parts  of  ether,  and 
in  20  parts  of  benzene. 

TESTS   OF  PURITY 

Resins:  Substances  Insoluble  in  Water.  —  1  gm.  of  picric  acid  should  dissolve 
completely  and  without  turbidity  in  100  c.c.  of  water.  On  adding  to  the  solution 
1  or  2  drops  of  16  per  cent  sulphuric  acid,  no  precipitate  should  form  on  standing 
fifteen  hours.  On  subsequently  filtering  the  liquid,  no  lesin  should  remain  on 
the  filter.  (Indicating  none  present.) 

Picrates  of  Potassium,  Sodium,  and  Ammonium.*  —  1  gm.  of  picric  acid 
must  completely  dissolve  in  20  c.c.  of  benzene,  affording  a  clear  solution.  (Indi- 
cating none  present.) 

Oxalic  Acid.  —  On  adding  calcium  chloride  solution  to  a  solution  of  1  gm. 
of  picric  acid  in  100  c.c.  of  water,  a  precipitate  ol  calcium  oxalate  should  not 
form  within  two  hours.  (Indicating  less  than  0.1  per  cent  EhC-/)^) 

Free  and  Combined  Sulphuric  Acid.  —  Evaporate  a  mixture  of  2  gm.  of 
picric  acid  and  10  c.c.  of  nitric  acid  (sp.gr.  1.4)  to  dryness  on  the  water-bath. 
Dissolve  the  residue  in  100  c.c.  of  boiling  water  with  the  addition  of  5  c.c.  of 
nitric  acid,  allow  to  cool,  then  filter,  and  add  barium  nitrate  solution  to  the 
filtrate.  There  should  be  no  immediate  turbidity.  (Indicating  less  than  0.25 
per  cent  SO3.) 

Inorganic  Matter  (Ash).  —  1  gm.  of  picric  acid  cautiously  incinerated  in  an 
open  platinum  dish  should  not  leave  a  residue  weighing  more  than  0.001  gm. 
(Indicating  less  than  0.1  per  cent.) 

Quantitative  Determination.  —  Titrate  1  gm.  of  picric  acid  dissolved  in 
100  c.c.  of  warm  water  with  fifth  normal  potassium  hydroxide  solution,  using 
phenolphthalein  as  indicator. 

1  c.c.  fifth  normal  KOH- 0.04581  gm.  C6H2(OH)(NO2)3;  log.  66096. 


*  Picric  acid  cannot  be  tested  for  ammonia  by  warming  with  sodium  hydroxide 
solution,  as  under  such  conditions  picric  acid  itself  decomposes  with  the  evolution 
of  ammonia. 


ACID  ROSOLIC  23 

ACID   ROSOLIC 

(Corallin) 
C20Hi6O3.    Mol.  Wt  304.12 

Brittle,  amorphous,  reddish-brown  pieces,  presenting  a  metallic 
luster,  and  readily  soluble  in  alcohol,  but  almost  insoluble  in  water. 

Rosolic  acid  is  used  as  an  indicator  in  the  form  of  a  solution 
of  0.5  gm.  of  the  acid  in  a  mixture  of  50  c.c.  of  alcohol  (about  85 
per  cent  by  weight)  and  50  c.c.  of  water. 

TEST   OF   SENSITIVENESS 

Add  2  or  3  drops  of  the  above  rosolic  acid  solution  to  100  c.c.  of  distilled 
vater.  On  adding  to  the  solution  0.05  c.c.  of  decinormal  potassium  hydroxide, 
the  pale-yellow  color  of  the  water  should  change  to  a  rose-red,  and  on  the  fur- 
ther addition  of  0.05  c.c.  of  decinormal  hydrochloric  acid,  the  original  color 
should  be  restored. 

ACID   SUCCINIC 
C4H6O4.     Mol.  Wt.  118.05 

Colorless,  monoclinic  prisms,  soluble  in  20  parts  of  cold  and 
about  2  parts  of  boiling  water;  in  10  parts  of  alcohol  and  in  80  parts 
of  ether.  Succinic  acid  melts  at  182°  C.,  and  at  235°  C.  it  boils 
with  the  evolution  of  white  acrid  fumes,  while  it  undergoes  decom- 
position to  a  large  extent  into  water  and  succinic  anhydride. 

TESTS  OF  PURITY 

Non- volatile  Matter.  —  1  gm.  of  succinic  acid  carefully  heated  in  a  platinum 
dish  should  volatilize  and  leave  no  weighable  residue;  nor  should  any  charring 
occur.  (Indicating  less  than  0.05  per  cent.)  The  acid  should  not  be  allowed 
to  burn. 

Oxalic  Acid.  —  The  solution  of  1  gm.  of  succinic  acid  in  20  c.c.  of  water 
should  not  be  affected  by  calcium  chloride  solution.  (Indicating  less  than  0.07 
per  cent  H2C2O4.) 

Tartaric  Acid. — Dissolve  5  gm.  of  succinic  acid  in  50  c.c.  of  warm  water,  add 
5  c.c.  of  potassium  acetate  solution,  and  then  mix  the  sohition  with  50  c.c.  of 
alcohol.  No  precipitate  should  form  on  standing  fifteen  hours.  (Indicating  less 
than  2  per  cent  H2C4H4O6.) 

Sulphates.  —  On  adding  barium  nitrate  solution  to  a  solution  of  1  gm.  of 
succinic  acid  in  20  c.c.  of  water,  no  precipitate  should  form  on  standing  fifteen 
hours.  (Indicating  less  than  0.001  per  cent  SO?.) 

Chlorides.  —  On  adding  2  or  3  c.c.  of  nitric  acid  to  20  c.c.  of  the  1  :  20 
aqueous  solution  of  succinic  acid,  not  more  than  a  faint  opalescent  turbidity 
should  develop  on  the  addition  of  silver  nitrate  solution.  (Indicating  less 
than  0.002  per  cent  Cl.) 


24  CHEMICAL  REAGENTS 

Ammonium  Salts.  —  1  gm.  of  succinic  acid,  on  being  heated  with  10  c.c.  of 
sodium  hydroxide  solution  (sp.gr.  1.3),  should  liberate  no  ammonia  (to  be 
ascertained  with  moist  litmus  paper).  (Indicating  less  than  0.0035  per  cent  NH3.) 

Heavy  Metals.  —  1  gm.  of  succinic  acid  dissolved  in  20  c.c.  of  water  should 
not  be  visibly  changed  by  hydrogen  sulphide  water.  (Indicating  none  present.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  succinic  acid  in  50  c.c. 
of  water,  and  titrate  with  normal  potassium  hydroxide,  using  phenolphthalein 
as  indicator. 

1  c.c.  of  normal  KOH  =  0.059025  gm.  of  C4H6O4,  log.  77103. 

ACID   SULPHANILIC 

C6H4(NH2)(S03H)i  :  4+2H2O.    Mol.  Wt.  209.17 

Sulphanilic  acid  occurs  in  colorless,  acicular,  efflorescent  crystals. 
It  has  no  melting-point,  but  carbonizes  on  being  heated  to  280°  to 
300°  C.  The  acid  is  difficultly  soluble  in  cold  water  (about  160 
parts),  but  more  readily  soluble  in  hot  water;  it  is  almost  insoluble 
in  alcohol,  ether,  and  benzene. 

TESTS   OF  PURITY 

Inorganic  Matter.  —  1  gm.  of  sulphanilic  acid  should  leave  no  weighable 
residue  on  ignition.  (Indicating  less  than  0.05  per  cent.) 

Sulphuric  Acid  (Aniline  Sulphate).  —  A  solution  of  1  gm.  of  sulphanilic  acid 
acid  in  25  c.c.  of  boiling  water  should  not  change  in  appearance  on  adding  a 
few  drops  of  barium  chloride  solution.  (Indicating  less  than  0.004  per  cent  SO3.) 

Hydrochloric  Acid  (Aniline  Hydrochloride). —  On  shaking  1  gm.  of  sul- 
phanilic acid  with  20  c.c.  of  water  and  filtering,  the  filtrate  should  exhibit  at  most 
a  faint  opalescent  turbidity  on  the  addition  of  a  few  drops  of  nitric  acid  and 
silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

ACID     SULPHURIC 

H2SO4.    Mol.  Wt.  98.09 

I 

ACID   SULPHURIC,  Sp.Gr.   1.84 
(Concentrated  Sulphuric  Acid) 

A  clear,  colorless,  oily  liquid  of  specific  gravity  1.84,  and  containing 
95  to  96  per  cent  of  H2S04. 

TESTS  OF  PURITY 

Non- volatile  Matter.  —  100  gm.  of  sulphuric  acid,  on  being  evaporated  and 
ignited,  should  leave  no  weighable  residue.  (Indicating  less  than  0.0005  per  cent.) 

Nitric  Acid.  —  Dilute  5  c.c.  of  sulphuric  acid  with  5  c.c.  of  water,  and  overlay 
this  liquid  on  5  c.c.  of  diphenylamine  solution  (see  Diphenylamine,  page  79). 
A  blue  zone  should  not  form  at  the  contact-surfaces  of  the  two  liquids  within 
one  hour.  (Indicating  less  than  0.0008  per  cent  N2O5.) 


ACID  SULPHURIC  25 


Selenium.  —  On  overlaying  2  c.c.  of  sulphuric  acid  with  2  c.c.  of  hydrochloric 
acid  in  which  a  granule  of  sodium  sulphite  has  been  dissolved,  a  reddish  zone 
must  not  form  at  the  contact-surfaces  of  the  two  liquids;  nor  should  a  red  pre- 
cipitate form  on  warming.  (Indicating  less  than  0.0033  per  cent  Se.) 

Substances  Oxidizable  by  Permanganate  (Nitrous  and  Sulphurous  Acids). 

—  Dilute  20  c.c.  of  sulphuric  acid  with  60  c.c.  of  water,  and  color  the  solution  by 

adding  1  drop  of  decinormal  potassium  permanganate  solution.     The  pink  color 

should  not  disappear  within  five  minutes.     (Indicating  less  than  0.001  per  cent 

as  S02.) 

Hydrogen-Halogen  Acids.  —  20  c.c.  of  sulphuric  acid  diluted  with  20  c.c.  of 
water  should  not  become  turbid  within  three  hours  on  adding  silver  nitrate 
solution.  (Indicating  less  than  0.0003  per  cent  as  Cl.) 

Lead.  —  On  cautiously  diluting  10  c.c.  of  sulphuric  acid  with  50  c.c.  of  alcohol 
(about  85  per  cent  by  weight),  no  turbidity  should  be  observed;  nor  should  a 
precipitate  of  lead  sulphate  form  on  standing  two  hours.  (Indicating  less  than 
0.003  per  cent  Pb.) 

Heavy  Metals  and  Calcium.  —  (a)  Dilute  10  c.c.  of  sulphuric  acid  with  50 
c.c.  of  water,  and  add  ammonia  water  in  excess.  On  now  adding  a  few  drops  of 
ammonium  sulphide  and  ammonium  oxalate  solutions,  neither  a  green  color  nor 
a  turbidity  should  appear.  (Indicating  no  heavy  metals  present,  and  less  than 
0.0055  per  cent  Ca.) 

(6)  On  diluting  20  c.c.  of  sulphuric  acid  with  100  c.c.  of  water,  and  passing 
a  current  of  hydrogen  sulphide  gas  into  the  solution,  no  brown  color  should 
develop,  nor  should  a  precipitate  form.  (Indicating  no  heavy  metals  present.) 

Ammonium  Salts.  —  Dilute  2  c.c.  of  sulphuric  acid  with  30  c.c.  of  water,  and 
add  aqueous  solution  of  potassium  hydroxide  (1  :  6)  to  alkalinity,  followed  by 
10  to  15  drops  of  Nessler's  reagent.  At  most  a  light-yellow  color  or  precipitate 
may  develop,  but  in  no  case  should  the  color  or  precipitate  be  brownish-red. 
(Indicating  less  than  0.0015  per  cent  NH3.) 

Arsenic.  —  Evaporate  200  gm.  of  the  acid  after  adding  a  few  cubic  centimeters 
of  nitric  acid  (1.40-1.42),  to  about  10  c.c.,  and  dilute  with  40  c.c.  of  water.  A 
Marsh  apparatus  is  set  in  operation,  using  20  gm.  of  arsenic-free,  granulated  zinc, 
and  arsenic-free,  dilute  sulphuric  acid  (1  :  5).  As  soon  as  the  air  has  been  expelled 
from  the  apparatus,  heat  the  reduction  tube  to  redness,  and  then  gradually  intro- 
duce the  cooled  acid  mixture  to  be  tested.  No  deposit  of  arsenic  should  be 
visible  in  the  reduction  tube  within  two  hours.  (Indicating  less  than  0.0000025 
per  cent  As.) 

Quantitative  Determination.  —  The  content  of  H2SO4  is  most  readily  ascer- 
tained by  taking  the  specific  gravity,  and  then  referring  to  tables  for  percentage. 
Consult  the  tables  of  Lunge,  Isler,  and  Naef,  Chem. -Tech.  Untersuch.-Meth.,  5 
ed.,  1,  354  (1904);  compare  Watts'  Diet,  of  Chem.,  4,  621  (1894);  also  J.  Soc. 
Chem.  Ind.,  24,  790  (1905)  and  Landolt-Bornstein-Roth,  Physikalisch-Chemische 
Tabellen,  4  ed.,  265  (1912).  The  acid  content  may  also  be  ascertained  by  diluting 
5  gm.  with  water  to  50  c.c.  and  titrating  10  c.c.  of  this  with  normal  potassium 
hydroxide  solution,  using  methyl  orange  as  indicator. 

1  c.c.  of  normal  KOH  =  0.049043  gm.  of  H2SO4,  log.  69057. 


II 
ACID   SULPHURIC,  DILUTED,   16  PER   CENT 

A  colorless  liquid  of  specific  gravity  1.110  to  1.114,  and  con- 
taining about  16  per  cent  of  H^SCU. 


26  CHEMICAL  REAGENTS 


TESTS  OF  PURITY 

The  tests  to  be  made  and  conditions  to  be  observed  are  those  given  under 
Acid  Sulphuric,  Sp.Gr.  1.84.  But  for  1  c.c.  of  the  acid  sp.gr.  1.84  use  6  c.c.  of 
the  acid  sp.gr.  1.110. 

(ACID)   SULPHURIC  ANHYDRIDE 
(Sulphur  Trioxide) 
SO3.    Mol.  Wt.  80.07 

Long,  transparent,  colorless  prisms,  which  melt  at  15°  C.  to  a 
clear  oily  liquid,  boiling  at  46°  C.  On  long  keeping  at  a  tempera- 
ture below  25°  C.,  the  sulphuric  anhydride  polymerizes  to  a  modifica- 
tion which  forms  long,  silky,  felted  needles,  which  melt  above  50° 
C.,  and  which  at  a  higher  temperature  become  converted  into  the 
trioxide  in  vapor  form,  solidifying  at  15°  C.,  and  boiling  at  46°  C. 

NOTE.  —  Regarding  the  quantitative  determination  of  sulphuric  anhydride, 
see  the  statements  given  under  Acid  Sulphuric,  Fuming.  Also  R.  Rosenlecher, 
"  The  Assay  of  Fuming  Sulphuric  Acid  and  of  Sulphuric  Anyhdride,"  Z.  anal. 
Chem.  37,  209  (1898);  dbst.,  J.  Chem.  Soc.,  74,  II,  404  (1898). 

ACID    SULPHURIC,    FUMING 

I 
ACID    SULPHURIC,    FUMING.    FREE    FROM    NITROGEN 

A  colorless,  oily  liquid,  fuming  in  the  air,  and  containing  8  to 
10  per  cent  of  free  SO3  (i.e.,  83.1  to  83.5  per  cent  total  SO*.) 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  3  c.c.  of  fuming  sulphuric  acid,  on  being  evaporated 
and  ignited,  should  leave  no  weighable  residue.  (Indicating  less  than  0.009 
per  cent.) 

Nitric  Acid.  —  Dilute  1  c.c.  of  fuming  sulphuric  acid  with  9  c.c.  of  water,  and 
overlay  the  fluid  on  5  c.c.  of  diphenylamine  solution  (see  Diphenylamine,  p.  79). 
No  blue  zone  should  form  at  the  contact-surfaces  of  the  two  liquids.  (Indicating 
less  than  0.004  per  cent  N2O5,  equivalent  to  0.001  per  cent  N.) 

Ammonium  Salts.  —  Carefully  add  2  c.c.  of  fuming  sulphuric  acid,  by  drops, 
to  30  c.c.  of  water,  and  add  aqueous  solution*  (1  :  6)  of  potassium  hydroxide 
to  alkalinity;  on  now  adding  10.  to  15  drops  of  Nessler's  reagent,  at  most  a 
pale  yellow,  but  in  no  case  may  a  brownish-red  color  or  precipitate  develop. 
(Indicating  less  than  0.002  per  cent  NH3.) 

Halogens.  —  Add  1  c.c.  of  fuming  sulphuric  acid,  by  drops,  to  30  c.c.  of 
water;  on  now  adding  a  few  drops  of  silver  nitrate  solution,  the  liquid  must  not 

*  Made  from  Potassium  Hydroxide,  Purest. 


ACID  SULPHURIC  27 


acquire  more  than  a  faint  opalescent  turbidity.  (Indicating  less  than  0.0015 
per  cent  as  Cl.) 

Lead.  —  On  cautiously  adding  10  c.c.  of  fuming  sulphuric  acid,  by  drops, 
to  50  c.c.  of  alcohol  (about  85  per  cent  by  weight),  a  clear  liquid  should  result, 
which  should  contain  no  precipitate  of  lead  sulphate  after  standing  two  hours. 
(Indicating  less  than  0.003  per  cent  Pb.) 

Arsenic.  —  A  Marsh  apparatus  is  set  in  operation,  using  20  gm.  of  arsenic- 
free,  granulated  zinc,  and  arsenic-free,  dilute  (1  :  5)  sulphuric  acid.  As  soon 
as  the  air  has  been  expelled  from  the  apparatus,  heat  the  reduction  tube  to 
redness,  then  run  into  the  apparatus  a  cooled  mixture  of  10  c.c.  of  the  fuming 
sulphuric  acid  with  90  c.c.  of  water.  No  deposit  of  arsenic  should  be  visible 
in  the  reduction  tube  within  an  hour.  (Indicating  less  than  0.0001  per  cent  As.) 

Quantitative  Determination.*  —  Weigh  off  accurately  1  gm.  of  fuming  sul- 
phuric acid  in  a  Lunge-Rey  stoppered  bulb  pipette,  f  and  cautiously  allow  the 
acid  to  run  into  10  c.c.  of  water,  contained  in  a  porcelain  dish.  The  contents 
of  the  dish  are  now  rinsed  into  a  measuring  flask  of  100  c.c.  capacity,  and  the 
flask  then  filled  up  with  water  to  the  mark.  After  vigorously  shaking,  25  c.c. 
of  the  liquid  are  titrated  with  fifth  normal  potassium  hydi  oxide  solution,  using 
methyl  orange  as  indicator,  J 

1  c.c.  of  fifth  normal  KOH  =  0.008007  gm.  of  SO3,  log.  90347. 


II 
ACID    SULPHURIC,    FUMING  § 

An  oily  liquid,  sometimes  slightly  colored,  and  often  not  perfectly 
clear.  The  acid  fumes  in  the  air,  contains  from  8  to  10  per  cent  of 
free  SOC,  and  is  intended  for  nitrogen  determinations  by  the  Kjeldahl 

method. 

TESTS   OF  PURITY 

Nitrogen.  —  Dilute  30  c.c.  of  the  fuming  sulphuric  acid  with  100  c.c.  of  water, 
add  3  gm.  of  zinc  dust,  and  allow  the  mixture  to  stand  with  frequent  stirring 
until  the  evolution  of  hydrogen  has  ceased.  Then  add  nitrogen-free  solution 
of  sodium  hydroxide  (sp.gr.  1.3)  until  strongly  alkaline,  and  distil,  collecting  the 
distillate  in  a  receiver  containing  about  10  c.c.  of  water  and  2  or  3  c.c.  of  fifth 


*  In  accurate  determinations,  the  acidity  due  to  sulphurous  acid  must  be 
deducted  from  that  determined  by  titration.  Regarding  this,  see  Lunge,  Chem.- 
tech.,  Untersuch.-Meth.,  5  ed.,  1,  395  (1904);  compare  J.  Chem.  Soc.,  68,  II, 
413  (1895). 

f  See  Lunge,  Chem.-tech.  Untersuch.-Meth.,  5  ed.,  1,  394  (1904);  illustrated 
in  trade  catalogues  of  glassware,  etc . 

t  In  order  to  ascertain  the  free  SO3  from  the  total  SO3  found  by  analysis, 
see  the  table  in  Lunge,  Chem.-tech.  Untersuch.-Meth.,  5  ed.,  1,  399  (1904); 
compare  Thorpe's  Die.  of  Appld.  Chem.,  2  ed.,  3,  711  (1895). 

§  This  acid,  which  contains  traces  of  nitric  acid,  is  considerably  cheaper  than 
the  foregoing  acid,  which  is  practically  free  from  nitrogen.  It  is  well  adapted  for 
use  in  laboratories  where  fuming  sulphuric  acid  is  very  frequently  used  for  the 
Kjeldahl  nitrogen  determinations.  For  accurate  nitrogen  determinations,  how- 
ever, it  will  be  necessary  to  determine  the  nitrogen  content  of  the  acid  by  a 
blank  test  carried  out  in  the  manner  above  described. 


28  CHEMICAL  REAGENTS 


normal  hydrochloric  acid.  The  distillate  is  then  titrated  with  fifth  normal 
potassium  hydroxide  solution,  using  methyl  orange  as  indicator.  To  neutralize 
the  ammonia  from  the  fuming  sulphuric  acid  should  not  require  more  than  0.2 
c.c.  of  the  fifth  normal  hydrochloric  acid.  (Indicating  not  more  than  0.001  per 
cent  N.) 

Quantitative  Determination.  —  The  determination  'is  carried  out  as  described 
under  Acid  Sulphuric,  Fuming,  Free  from  Nitrogen. 

ACID   SULPHURIC,  WITH  PHOSPHORIC  ANHYDRIDE 

Approximately  10,  15,  or  20  per  cent  PzO5 

Sulphuric  acid  containing  phosphorus  pentoxide.  Approximately 
10,  15,  or  20  per  cent  of  ?205  are  the  usual  strengths.  The  prep- 
aration is  employed  in  Kjeldahl's  nitrogen  determination. 

TESTS   OF  PURITY 

Nitric  Acid.  —  Dilute  1  c.c.  of  the  solution  of  phosphoric  anhydride  in  sul- 
phuric acid  with  9  c.c.  of  water,  and  overlay  this  fluid  on  5  c.c.  of  diphenylamine 
solution  (see  Diphenylamine,  page  79).  No  blue  zone  should  form  at  the 
contact-surfaces  of  the  two  liquids.  (Indicating  less  than  0.004  per  cent  ^Os.) 

Ammonium  Salts.  —  Dilute  2  c  c.  of  the  solution  of  phosphoric  anhydride 
in  sulphuric  acid  with  30  c.c.  of  water,  and  add  aqueous  solution*  of  potassium 
hydroxide  (1  :  6)  to  alkalinity,  followed  by  10  to  15  drops  of  Nessler's  reagent. 
At  most  only  a  faint  yellow,  but  in  no  case  a  brownish-red,  color  or  precipitate 
should  form.  (Indicating  less  than  0.002  per  cent  NH8.) 

ACID    SULPHURIC,   FUMING,   WITH  PHOSPHORIC 
ANHYDRIDE 

Approximately  5,  10,  15,  20,  or  25  per  cent  P205 

Fuming  sulphuric  acid  containing  phosphorus  pentoxide;  the 
usual  grades  contain  approximately  5,  10,  15,  20,  or  25  per  cent  of 
P2Os.  The  preparation  is  used  in  Kjeldahl's  nitrogen  determination. 

TEST   OF  PURITY 

Nitrogen.  —  The  nitrogen  determination  is  carried  out  as  described  under 
Acid  Sulphuric,  Fuming.  See  footnote  there. 

ACID   SULPHUROUS 
SO2+Aq.     Mol.  Wt.  64.07 

A  clear,  colorless  liquid  of  specific  gravity  1.029  to  1.035.  The 
acid  first  reddens  blue  litmus  paper,  and  then  bleaches  it.  The 
liquid  contains  about  6  per  cent  of  862 . 


Made  from  Potassium  Hydroxide,  Purest. 


CUBES  FOR  GENERATING  SULPHUROUS  ACID  29 


TESTS   OF  PURITY 

Non-volatile  Matter.  —  10  c.c.  of  sulphurous  acid,  on  being  evaporated  and 
ignited,  should  leave  no  weighable  residue.  (Indicating  less  than  0.048  per 
cent.) 

Quantitative  Determination.  —  Weigh  off  10  gm.  of  sulphurous  acid  in  a 
measuring  flask  of  100  c.c.  capacity,  and  fill  with  boiled  water  up  to  the  mark. 
Allow  the  fluid  to  run  from  a  burette  into  30  c.c.  of  decinormal  iodine  solution, 
constantly  shaken,  until  decoloration  ensues.  To  effect  this  not  more  than 
16.2  c.c.  of  the  acid  solution  should  be  required. 

1  c.c.  of  decinormal  1=0.003205  gm.  of  SO2,  log.  50562. 

ACID,   SULPHUROUS;    CUBES  FOR  GENERATING 

Cube-like  pieces,  containing  at  least  30  per  cent  of  862. 
TEST   OF   STRENGTH 

Quantitative  Determination.  —  Introduce  1  gm.  of  the  finely  powdered  cubes 
and  5  gm.  of  anhydrous  sodium  carbonate  into  a  graduated  flask  of  100  c.c. 
capacity;  add  50  c.c.  of  water,  boil  the  mixture  for  about  ten  minutes,  allow  to 
cool,  fill  the  flask  up  to  the  mark,  mix,  and  filter.  Run  the  filtrate  from  a 
burette  into  a  constantly  shaken  mixture  of  30  c.c.  of  decinormal  iodine  solu- 
tion and  10  c.c.  of  hydrochloric  acid,  until  complete  decoloration  ensues. 

1  c.c.  of  decinormal  1  =  0.003205  gm.  of  SO2,  log.  50562. 


ACID  TANNIC 

(Tannin) 
Ci4H10O9+2H2O.    Mol.  Wt.  358.11 

A  yellowish  powder,  or  crystal-like  lustrous  scales.  Tannic  acid 
is  soluble  in  1  part  of  water  and  in  2  parts  of  alcohol  (about  85  per 
cent  by  weight),  yielding  a  clear  liquid  acid  to  litmus  paper.  Tannic 
acid  is  also  soluble  in  about  8  parts  of  glycerin,  but  is  difficultly 
soluble  in  ether*  (of  sp.gr.  0.720).  Solutions  of  tannic  acid  are 

dextrorotary. 

TESTS   OF  PURITY 

Inorganic  Matter  (Zinc).  —  4  gm.  of  tannin  on  ignition  should  not  leave  a 
residue  exceeding  0.005  gm.  in  weight.  (Indicating  less  than  0.125  per  cent 
inorganic  matter.)  If  this  residue  is  dissolved  in  2  c.c.  of  acetic  acid,  then 
diluted  with  8  c.c.  of  water  and  filtered,  the  filtrate  should  not  show  more  than 
a  slight  opalescent  turbidity  when  treated  with  hydrogen  sulphide  water.  (Indi- 
cating less  than  0.006  per  cent  Zn.) 

Sugar,  Dextrin.  —  On  mixing  10  c.c.  of  an  aqueous  (1  :  5)  solution  of  tannic 
acid  with  10  c.c.  of  alcohol  (about  85  per  cent  by  weight)  the  mixture  must 


*  The  solubility  in  ether  depends  very  largely  upon  the  amount  of  alcohol 
in  the  ether. 


30  CHEMICAL  REAGENTS 


remain  clear  for  one  hour;  and  no  turbidity  should  occur  on  the  further  addition 
of  5  c.c.  of  ether.  (Indicating  none  present.) 

Water.  —  On  drying  tannic  acid  at  100°  C.,  it  should  not  lose  more  than 
12  per  cent  of  its  weight. 

NOTE.  —  Regarding  the  quantitative  determination  of  tannic  acid  see 
Fresenius,  Anleitung  zur  quantitativen  Analyse,  6  ed.,  2,  619,  or  Lunge,  Chem.- 
tech.  Untersuch.-Meth.,  5  ed.,  3,  698  ff.  (1905);  Fresenius-Cohn,  Quantitative 
Analysis,  2,  767  ff.  (1904).  Compare  Allen's  Commercial  Organic  Analysis, 
4  ed.,  5,  57  ff.  (1911). 

ACID  TARTARIC 
C4H6O6.    Mol.  Wt.  150.05 

Colorless,  prismatic  crystals,  or  crystalline  crusts,  soluble  in  0.8 
part  of  water,  and  in  4  parts  of  alcohol  (about  85  per  cent  by  weight) . 
TESTS  OF  PURITY 

Sulphuric  Acid  and  Calcium.  —  Separate  20  c.c.  portions  of  the  aqueous 
(1  :  10)  solution  of  the  acid  should  show  no  change  with  barium  chloride  or 
ammonium  oxalate  solution.  (Indicating  less  than  0.005  per  cent  SO3,  and 
less  than  0.01  per  cent  Ca.) 

Oxalic  Acid.  —  A  solution  of  2  gm.  of  the  acid  in  20  c.c.  of  water  when  brought 
to  only  slight  acidity  by  adding  ammonia  water,  should  show  no  .change  on 
adding  calcium  sulphate  solution.  (Indicating  less  than  0.035  per  cent  H2C2O4.) 

Lead*  and  Other  Metals.  —  (a)  The  solution  of  5  gm.  of  tartaric  acid  in  20 
c.c.  of  water  with  12  c.c.  of  ammonia  water  added,  should  not  develop  a  brown 
color  on  the  addition  of  hydrogen  sulphide  water.  (Indicating  none  present.) 

(6)  20  c.c.  of  the  1  :  10  aqueous  solution  should  not  be  affected  by  hydrogen 
sulphide  water.  (Indicating  none  present.) 

Inorganic  Matter.  —  1  gm.  of  tartaric  acid,  on  being  ignited,  should  leave 
no  weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  tartaric  acid  in  50  c.c.  of 
water,  and  titrate  with  normal  sodium  hydroxide  solution,  using  phenolphthalein 
as  indicator. 

1  c.c.  of  normal  NaOH  =  0.075025  gm.  of  C4H6O6,  log.  87520. 

ACID   THIOACETIC    SOLUTION 

CH3COSH.     Mol.  Wt.  70.10 

A  6  per  cent  aqueous  solution  used  instead  of  hydrogen  sulphide 
in  chemical  analysis,  f  The  concentrated  acid  is  soluble  in  16  parts 
of  water,  and  easily  in  alcohol.  It  is  a  yellow  liquid  of  penetrating 
odor,  boiling  between  92°  and  97°  C.,  and  having  a  specific  gravity 
of  1.070. 


*Regaiding  the  examination  of  tartaric  acid  for  lead  see  Tatlock  and  Thomp- 
son, Analyst,  33,  173  (1908);  abst.,  C.  A.  2,  2269  (1908). 

t  Regarding  the  use  of  thioacetic  acid,  see  the  following:  R.  Schiff  and 
N.  P.  Tarugi,  Ber.,  27,  3437  -(1894);  dbst.,  J.  Chem.  Soc.,  68,  II,  84  (1895).  R. 
Schiff,  Ber.,  28,  1204  (1895)  [or  Z.  anal.  Chem.,  34,  456  (1895)];  abst.,  J.  Chem. 
Soc.,  68,  II,  370  (1895). 


ALCOHOL    AMYLIC  31 

TESTS   OF  PURITY 

Non-volatile  Matter.  — •  10  c.c.  of  thiaacetic  acid  solution,  on  being  evaporated 
and  ignited,  should  leave  no  weighable  residue.  (Indicating  less  than  0.0047  per 

Sulphuric  Acid.  —  On  mixing  5  c.c.  of  thioacetic  ?cid  solulion  wLh  100  c.c.  of 
water,  and  adding  barium  chloride  solution,  no  turbidity  should  occur.  (Indicat- 
ing less  than  0.003  per  cent  SOs.) 


ALCOHOL    AMYLIC 
CsHuOH.    Mol.  Wt.  88.10 

I 

i 

AMYL    ALCOHOL 

(Iso-Amyl  Alcohol) 

A  clear,  colorless  liquid,  neutral  to  litmus  paper.  Amyl  alcohol 
is  but  slightly  soluble  in  water,  but  is  clearly  miscible  with  alcohol, 
ether,  and  benzene.  It  has  a  specific  gravity  of  0.814  and  boils 

at  131°  C. 

TESTS   OF  PURITY 

Non-volatile  Matter.  — 10  gm.  of  amyl  alcohol  evaporated  on  the  water- 
bath  should  leave  no  weighable  residue.  (Indicating  less  than  0.005  per  cent.) 

Foreign  Organic  Matter  (Furfural,  etc.).  —  (a)  On  shaking  5  c.c.  of  amyl 
alcohol  with  5  c.c.  of  concentrated  sulphuric  acid,  the  mixture  should  not  acquire 
more  than  a  faint  yellow  or  reddish  color.  (Indicating  none  present.) 

(6)  On  shaking  5  c.c.  of  amyl  alcohol  with  5  c.c.  of  potassium  hydroxide 
solution  (sp.gr.  1.3),  the  amyl  alcohol  should  not  acquire  any  color.  (Indicating 
none  present.) 

II 
AMYL    ALCOHOL    FOR    GERBER'S    FAT    DETERMINATION 

A  colorless  liquid  boiling  at  129°  to  132°  C.,  and  of  specific  grav- 
ity about  0.815. 

TEST   OF  PURITY 

1  c.c.  of  amyl  alcohol  shaken  with  10  c.c.  of  concentrated  sulphuric  acid, 
(sp.gr.  1.820  to  1.825)  and  11  c.c.  of  water  in  a  Gerber  butyrometer,  then  centri- 
fuged  for  two  or  three  minutes,  and  then  allowed  to  stand  for  twenty-four 
hours,  must  not  exhibit  an  oily  segregate.* 


*  Compare  N.  Gerber  and  M.  M.  Craandijk,  Milch  Ztg.,  27,  611  (1898). 
Chem.  Zentr.,  (5),  2,  II,  907  (1898). 


32  CHEMICAL  REAGENTS 

i  '  • 

ALCOHOL    ETHYLIC 
C2H6OH.    Mol.  Wt.  46.05 

I 
ALCOHOL   ABSOLUTE 

A  clear,  colorless  liquid  of  specific  gravity  not  over  0.797,  cor- 
responding to  at  least  99.46  per  cent  by  volume,  or  99.11  per  cent  by 
weight,  of  anhydrous  alcohol,  C2H5OH.  It  boils  at  78°  C.,  and 
should  not  affect  litmus  paper. 

TESTS   OF  PURITY 

Residue.  —  50  c.c.  of  alcohol,  on  being  slowly  evaporated,  should  leave  no 
residue.  (Indicating  none  present.) 

Fusel  Oil.*  —  On  mixing  10  c.c.  of  alcohol  and  30  c.c.  of  water  in  an  Erlen- 
meyer  flask,  no  turbidity  or  coloration  should  be  observed,  nor  should  any 
foreign  odor  be  noticeable.  (Indicating  none  present.) 

A  mixture  of  10  c.c.  of  alcohol  and  0.2  c.c.  of  15  per  cent  potassium 
hydroxide  solution,  when  evaporated  down  to  1  c.c.,  and  supersaturated  with 
dilute  sulphuric  acid,  should  not  have  the  odor  of  fusel  oil.  (Indicating  none 
present.) 

On  rubbing  a  few  drops  of  alcohol  between  the  hands,  no  unpleasant  odor 
should  be  noticeable.  (Indicating  none  present.) 

Dilute  5  c.c.  of  alcohol  with  5  c.c.  of  water  and  then  add  25  to  30  drops  of 
an  alcoholic  solution  of  salicylaldehyde  (1  :  100),  following  this  with  the  addition 
of  20  c.c.  of  concentrated  sulphuric  acid.  The  mixture  after  cooling  must  show 
no  reddish  or  garnet-red  color,  f  (Indicating  none  present.) 

Molasses-alcohol.  —  On  overlaying  5  c.c.  of  alcohol  on  5  c.c.  of  concentrated 
sulphuric  acid,  no  rose-red  zone  should  form  within  one  hour  at  the  contact- 
surfaces  of  the  two  liquids.  (Indicating  none  present.) 

Aldehyde.  — A  mixture  of  10  c.c.  of  alcohol  with  10  c.c.  of  water  and  2  c.c.  of 
ammoniacal  silver  nitrate  solution  |  protected  from  the  light  should  show  neither 
a  turbidity  nor  a  color  within  fifteen  hours.  (Indicating  none  present.) 

Organic  Impurities. §  —  The  red  color  of  a  mixture  of  10  c.c.  of  alcohol  and 
1  drop  of  a  1  :  1000  potassium  permanganate  solution  should  not  pass  into  yellow 
within  ten  minutes.  (Indicating  none  present.) 


*  Regarding  the  quantitative  determination  of  fusel  oil,  see  Lunge,  Chem.- 
tech.  Untersuch.-Meth.,  5  ed.,  3,  571  ff.  (1905);  compare  Allen's  Commercial 
Organic  Analysis,  4  ed.  Vol.  I,  p.  188  ff,  (1909). 

t  If  the  alcohol  is  free  from  fusel  oil  the  mixture  after  cooling  is  lemon-yellow. 
The  presence  of  the  slightest  trace  of  fusel  oil  gives  the  mixture  a  yellow  color 
by  transmitted  light  and  a  reddish  color  by  reflected  light. 

$  Made  by  mixing  10  c.c.  of  silver  nitrate  solution  (1  :  20)  with  5  c.c.  of 
ammonia  water. 

§  A  partial  decoloration  of  potassium  permanganate  occurs  even  with  purest 
alcohol.  Compare  also  M.  E.  Barbet,  J.  Pharm.  Chim.  19,  413,  457  (1889) 
or  Pharm.  Ztg.,  34,  481  (1889).  P.  Cazeneuve,  Chem.  Ztg.,  13,  Rep.  198  (1889); 
for  similar  article  see  J.  Chem.  Soc.,  56,  928  (1889).  Lang,  Chem.  Ztg.,  17,  1544 
(1893). 


ALCOHOL  33 


Metals  and  Tannin.  —  On  adding  to  10  c.c.  of  alcohol  1  c.c.  of  ammonia 
water  or  5  c.c.  of  hydrogen  sulphide  water,  no  coloration  should  develop.  (Indi- 
cating none  present.) 

Acetone.  —  Shake  for  one  minute  a  mixture  of  6  c.c.  of  baryta  water,  6  drops 
of  mercuric  chloride  solution  (1  :  20),  and  2  c.c.  of  alcohol;  then  filter.  The 
clear  filtrate  must  not  show  a  dark  color  upon  the  addition  of  solution  of  ammo- 
nium sulphide.  (Indicating  less  than  0.02  per  cent.) 

Furfural.  —  A  mixture  of  10  c.c.  of  alcohol,  1  drop  of  aniline,  and  5  drops 
of  diluted  acetic  acid  (about  30  per  cent)  should  show  no  red  color  upon  standing 
one  hour.  (Indicating  less  than  0.0001  per  cent.) 

NOTE.  —  On  the  estimation  of  methyl  alcohol  in  the  presence  of  ethyl  alcohol 
see  T.  E.  Thorpe  and  J.  Holmes,  J.  Chem.  Soc.,  85,  I,  1,  (1904). 

II 
ALCOHOL,    95   PER    CENT 

A  clear,  colorless  liquid  having  a  sp.gr.  of  about  0.816  at  15.6°  C., 
corresponding  to  about  95  per  cent  by  volume  of  anydrous  alcohol, 
C2H50H.  It  should  not  affect  the  color  of  litmus  paper. 

TESTS   OF  PURITY 

The  tests  of  purity  to  be  applied  and  the  conditions  to  be  observed  are  those 
given  under  Alcohol  Absolute. 

Ill 
ALCOHOL,   90   PER   CENT 

This  alcohol  has  a  specific  gravity  of  0.830  to  0.834,  and  con- 
tains 87.35  to  85.80  per  cent  of  alcohol  by  weight,  or  91.29  to  90.09 
per  cent  by  volume  of  anhydrous  alcohol,  C2H50H. 

TESTS   OF  PURITY 

The  tests  of  purity  to  be  applied  and  the  conditions  to  be  observed  are  those 
given  under  Alcohol  Absolute. 

ALCOHOL  METHYLIC 
CH3OH.    Mol.  Wt.  32.03 

A  colorless,  mobile  liquid,  readily  miscible  in  all  proportions 
with  water,  alcohol,  and  ether.  Methyl  alcohol  has  the  specific 
gravity  0.798,  and  boils  between  65°  and  66°  C.  It  should  not 
redden  blue  litmus  paper. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  30  c.c.  of  methyl  alcohol  evaporated  on  the  water- 
bath  should  leave  no  weighable  residue.  (Indicating  less  than  0.002  per  cent.) 


34  CHEMICAL  REAGENTS 


Acetone  and  Ethyl  Alcohol.  —  Shake  together  thoroughly  50  c.c.  of  double 
normal  sodium  hydroxide  solution  and  5  c.c.  of  methyl  alcohol  in  a  mixing 
cylinder,  and  add,  with  repeated  shaking,  25  c.c.  of  double  normal  iodine  solution. 
No  turbidity  or  flocculent  precipitate  should  occur;  nor  should  an  odor  of 
iodoform  be  perceptible  even  after  warming  the  mixture  at  above  60°  C.  for 
half  an  hour.  (Indicating  less  than  0.015  per  cent  acetone,  and  less  than  1  per 
cent  ethyl  alcohol.) 

Empyreumatic  Substances.  —  1  c.c.  of  methyl  alcohol  should  dissolve  without 
turbidity  in  10  c.c.  of  water.  (Indicating  none  present.) 

On  allowing  5  c.c.  of  concentrated  sulphuric  acid  to  drop  into  5  c.c.  of  methyl 
alcohol  while  kept  cold,  the  mixture  should  not  acquire  more  than  a  slightly 
yellowish  color.  (Indicating  none  present.) 

Aldehydes.  —  On  shaking  10  c.c.  of  methyl  alcohol  with  10  c.c.  of  sodium 
hydroxide  solution  (sp.gr.  1.3),  the  mixture  should  remain  colorless.  (Indicating 
none  present.) 

Substances  Oxidizable  by  Permanganate.  —  On  adding  1  drop  of  decinormal 
potassium  permanganate  solution  to  10  c.c.  methyl  alcohol,  the  red  color  of 
the  liquid  must  not  disappear  within  ten  minutes.  (Indicating  none  present.) 

Chloroform.  —  No  odor  of  isonitrile  should  be  developed  upon  bringing  to 
boiling  a  mixture  of  10  c.c.  of  methyl  alcohol  with  2  or  3  drops  of  aniline  and 
10  c.c.  of  alcoholic  solution  of  potassium  hydroxide  (1  :  10).  (Indicating  less 
than  0.01  per  cent  CHC13.) 

NOTE.  —  Regarding  the  quantitative  determination  of  methyl  alcohol,  as 
well  as  the  quantitative  determination  of  acetone  in  methyl  alcohol,  see  Lunge, 
Chem.-tech.  Untersuch.-Meth.,  6  ed.,  3,  970,  972  (1911).  Compare  Allen's 
Commercial  Organic  Analysis,  4  ed.,  1,  91  (1909).  Also  G.  Kramer,  H.  Strache, 
and  J.  Messinger  as  given  in  note  under  Acetone,  p.  1. 

ALPHANAPHTHOL 
Ci0H7OH.    Mol.  Wt.  144.06 

Colorless,  lustrous  needles,  having  a  phenolic  odor,  and  melting 
at  97°  C.  Alphanaphthol  is  difficultly  soluble  in  cold  water,  more 
readily  in  warm  water,  and  dissolves  easily  in  alcohol,  ether,  benzene 

and  chloroform. 

TESTS   OF  PURITY 

Organic  Acids.  —  Shake  1  gm.  of  alphanaphthol  with  100  c.c.  of  water  and 
filter.  The  nitrate  should  not  redden  blue  litmus  paper.  (Indicating  none 
present.) 

Organic  Substances  Insoluble  in  Sodium  Hydroxide  Solution.  —  1  gm.  of 
alphanaphthol  should  dissolve  completely  and  clearly  in  a  mixture  of  5  c.c.  of 
sodium  hydroxide  solution  III,  and  5  c.c.  of  water.  (Indicating  none  present.) 

Inorganic  Matter.  —  No  weighable  residue  should  remain  on  igniting  1  gm. 
of  alphanaphthol.  (Indicating  less  than  0.05  per  cent.) 

ALPHANAPHTHYLAMINE 

CioH7NH2.    Mol.  Wt.  143-08 

A  white,  crystalline  powder,  quickly  becoming  reddish  in  the  air; 
almost  insoluble  in  water,  easily  soluble  in  alcohol  and  in  ether,  and 
melting  at  50°  C. 


ALUMINUM  OXIDE  35 


TESTS  OF  PURITY 

Solubility.  —  0.5  gm.  of  alphanaphthylamine  should  dissolve  in  25  c.c.  of 
diluted  acetic  acid,  forming  a  clear  and  colorless  solution. 

Non-volatile  Matter.  —  On  heating,  1  gm.  of  alphanaphthylamine  should 
volatilize,  leaving  no  weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

ALUMINUM   OXIDE 

A12O3.    Mol.  Wt.  102.2 

A  white,  or  nearly  white,  very  bulky,  hygroscopic  powder,* 
used  for  Wislicenus'f  determination  of  tannin  and  colors.  Under  a 
microscope  magnifying  about  30  to  60  diameters  the  powder 
appears  in  the  form  of  partly  transparent,  flocculent  masses,  often 
fibrous-like,  resembling  vegetable  tissue. 

TESTS  OF  PURITY 

Metallic  Mercury  and  Aluminum.  —  On  moistening  the  preparation  with 
water  or  alcohol,  it  acquires  a  gray  color  if  any  aluminum  or  mercury  is  present; 
if  pure,  it  remains  perfectly  white.  No  globules  of  mercury  or  particles  of 
metallic  aluminum  should  be  visible  under  the  microscope.  (Indicating  none 
present.) 

Absorptive  Power  for  Tannin  and  Colors.  —  1  gm.  of  aluminum  oxide  freshly 
heated  (by  the  method  in  the  footnote)  is  vigorously  shaken  for  five  minutes 
with  200  c.c.  of  a  solution  of  4.5  gm.  of  pure  hydrated  tannin  (corresponding  to 
3.9  gm.  of  water-free  tannin)  or  about  the  same  amount  of  purified  congo  red 
(free  from  chloride  and  sulphate  of  sodium)  in  sufficient  water  to  make  1000 
c.c.  (Use  a  flask  with  a  rubber  stopper.)  The  mixture  is  at  once  heated  for 
five  minutes  on  the  water-bath,  and  filtered  through  a  paper  9  cm.  in  diameter. 
After  rejecting  the  first  10  c.c.  of  the  filtrate,  50  c.c.  are  evaporated  in  a  weighed 
Philips'  nickel  disht  and  the  residue  dried  in  a  water-bath  drying  oven  (Moslinger 
oven)  four  hours,  after  which  it  is  allowed  to  stand  an  hour  and  a  half  in  a  closed 
dish  in  a  desiccator,  and  is  then  weighed. 

The  total  residue  obtained  in  the  same  manner  from  50  c.c.  of  the  original 
tannin  or  dye  solution,  is  also  ascertained.  On  now  calculating  the  residue 
for  200  c.c.  of  original  solution,  and  deducting  from  this  the  total  residue  left 
from  the  solution  treated  with  the  aluminum  oxide,  the  result  should  show  that 
1  gm.  of  aluminum  oxide  absorbs  0.40  to  0.50  gm.  of  tannin,  or  0.035  to  0.045  gm. 
of  congo  red. 

*The  preparation,  just  before  use  for  quantitative  absorption  analysis 
must  always  be  heated  over  a  free  flame  until  the  bottom  of  the  dish  or  crucible 
just  begins  to  be  red.  Higher  or  longer  heating  reduces  the  absorptive  power. 
If  heated  in  rather  thick  layers  the  powder  must  take  on  a  ''boiling  or  seething" 
motion,  and  before  quieting  down  must  show  the  so-called  crater  formations. 

t  H.  Wislicenus,  Determination  of  Tannin  without  Hide  Powder,  Z.  angew. 
Chem.,  17,  801  (1904);  abst.,  J.  Soc.  Chem.  Ind.,  23,  765  (1904).  Z.  anal. 
Chem.,  44,  96  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  363  (1905).  Z.  Chem.  Ind. 
Kolloide,  2,  Supplementheft,  II,  XI,  (1908);  abst.,  J.  Chem.  Soc.,  94,  II,  261 
(1908).  H.  Wislicenus  and  W.  Muth,  Collegium,  No.  225,  157,  No.  256,  168; 
abst.,  C.  A.,  1,  2038  (1907). 

t  Pure  nickel  dish  8.5  cm.  in  diameter,  with  vertical  sides  2.5  cm.  high,  and 
with  a  grooved,  tightly-fitting  cover. 


36  CHEMICAL  REAGENTS 


AMMONIA    WATER 
NH3+H2O.     Mol.  Wt.  NH3  =  17.06 

The  aqueous  solution  of  ammonia  gas  is  a  clear,  colorless  liquid,. 
the  specific  gravity  of  which  decreases  as  the  ammonia  content 
increases. 

For  analytical  purposes,  two  solutions  of  different  concentration 
are  ordinarily  used,  of  which  one  has  a  specific  gravity  of  about 
0.96,  and  contains  about  10  per  cent  of  NHs,  while  the  other,  the 
concentrated,  has  the  specific  gravity  of  about  0.925,  and  contains 
about  20  per  cent  of  NHa.  In  American  laboratories  a  still  more 
concentrated  solution  of  ammonia  is  employed.  Its  strength  is 
about  28  per  cent  and  it  is  generally  designated  as  ''Stronger  Ammonia 
Water." 

I 

AMMONIA  WATER,   28  PER  CENT 
(Stronger  Ammonia  Water) 

A  clear,  colorless  liquid  having  a  specific  gravity  of  about  0.90 
and  containing  about  28  per  cent 


TESTS   OF  PURITY 

Non-volatile  Matter.  —  On  evaporating  3.5  c.c.  of  the  ammonia  water  on  the 
watei-bath,  no  weighable  residue  should  remain.  A  trace  of  residue,  however, 
is  almost  always  left.  (Indicating  less  than  0.016  per  cent.) 

Chlorides.  —  Dilute  3.5  c.c.  of  the  ammonia  water  with  30  c.c.  of  water,  and 
supersaturate  with  20  c.c.  of  nitric  acid.  This  liquid  should  show  no  change  on 
the  addition  of  silver  nitrate  solution.  (Indicating  less  than  0.0003  per  cent  Cl.) 

Pyridine.  —  Not  more  than  a  faint  odor  of  pyridine  should  be  perceptible 
on  diluting  20  c.c.  of  ammonia  water  with  20  c.c.  of  water  and  nearly  neutralizing 
with  dilute  sulphuric  acid  (1  :  4).  (Indicating  at  most  a  trace  present.) 

Tar-bases  (Aniline,  Pyridine,  Pyrrol,  etc.).  —  Evaporate  a  mixture  of  3.5 
c.c.  of  the  ammonia  water  and  20  c.c.  of  nitric  acid  on  the  water-bath.  The  residue 
on  evaporation  should  have  a  pure  white  color.  (Indicating  none  present.) 

Heavy  Metals.  —  On  diluting  2  c.c.  of  the  ammonia  water  with  20  c.c.  of 
water,  and  then  adding  a  few  drops  of  ammonium  sulphide  solution,  no  change 
should  appear.  (Indicating  none  present.) 

Sulphates.  —  Slightly  acidify  3.5  c.c.  of  the  ammonia  water  with  hydrochloric 
acid,  and  add  barium  chloride  solution.  No  precipitate  of  barium  sulphate 
should  form  on  standing  fifteen  hours.  (Indicating  less  than  0.0025  per  cent  SOs.) 

Carbon  Dioxide.  —  A  mixture  of  7  c.c.  of  the  ammonia  water  with  20  c.c.  of 
calcium  hydroxide  solution  should  not  become  more  than  very  slightly  turbid 
on  boiling.  (Indicating  less  than  0.015  per  cent  CO2.) 

Sulphides.  —  On  adding  a  few  drops  of  an  ammoniacal  lead  acetate  solution 


AMMONIA  WATER  37 

to  3.5  c.c.  of  the  ammonia  water,  the  liquid  must  not  acquire  a  yellow  or  a  brown 
color,  nor  should  a  dark  precipitate  form.  (Indicating  less  than  0.001  per 
cent  S.) 

Calcium.  —  A  mixture  of  3.5  c.c.  of  the  ammonia  water  with  20  c.c.  of  water 
should  exhibit  no  turbidity  on  the  addition  of  ammonium  oxalate  solution. 
(Indicating  less  than  0.002  per  cent  Ca.) 

Magnesium.  —  On  adding  ammonium  phosphate  solution  to  7  c.c.  of  the 
ammonia  water,  diluted  to  20  c.c.,  no  precipitate  should  form  on  standing  two 
hours.  (Indicating  less  than  0.001  per  cent  Mg.) 

Phosphates.  —  To  7  c.c.  of  the  ammonia  water  add  40  c.c.  of  nitric  acid  and 
25  c.c.  of  ammonium  molybdate  solution.  No  yellow  precipitate  should  form  in 
the  liquid  on  standing  two  hours  at  about  40°  C.  .(Indicating  less  than  0.0015 
per  cent  PzQs.) 

Substances  Oxidizable  by  Potassium  Permanganate.  —  To  a  mixture  of  7 
c.c.  of  ammonia  water  and  40  c.c.  of  water,  add  40  c.c.  of  diluted  sulphuric  acid 
and  0.1  c.c.  of  decinormal  potassium  permanganate  solution.  The*- pink  color 
of  the  liquid  should  not  disappear  on  boiling  five  minutes.  (Indicating  none 
present.) 

Quantitative  Determination.  —  Dilute  2  gm.  of  the  ammonia  water  with 
about  50  c.c.  of  water,  and  titrate  with  normal  solution  of  hydrochloric  acid, 
using  methyl  orange  as  indicator. 

1  c.c.  normal  HC1=0.017C3  gm.  NH3,  log.  23121. 

II 
AMMONIA  WATER,  20  PER  GENT 

(Concentrated  Ammonia  Water) 
This  solution  of  ammonia  has  the  specific  gravity  0.925,  and  con- 


tains  about  20  per  cent  of 

TESTS   OF  PURITY 

The  tests  of  purity  are  the  same  as  those  given  under  Ammonia  Water,  28 
per  cent.  But  instead  of  using  2  c.c.,  3.5  c.c.,  and  7  c.c.  of  the  28  per  cent,  use 
2.5  c.c..  5  c.c.  and  10  c.c.  respectively  of  the  20  per  cent  ammonia  water. 

Ill 

AMMONIA  WATER,   10  PER   CENT 

This  is  the  article  termed  "  Ammonia  Water  "  throughout  the 
text  of  this  book.  It  contains  about  10  per  cent  of  NHs,  and  has  a 
specific  gravity  about  0.96. 

TESTS   OF  PURITY 

The  tests  of  purity  are  the  same  as  those  given  under  Ammonia  Water,  28 
per  cent.  But  instead  of  using  2  c.c.,  3.5  c.c.,  and  7  c.c.,  of  the  28  per  cent,  use 
5  c.c.,  10  c.c.,  and  20  c.c.  respectively  of  the  10  per  cent  ammonia  water. 


38  CHEMICAL  REAGENTS 


AMMONIUM  ACETATE 
NH4C2H3O2.     Mol.  Wt.  77.07 

A  white,  hygroscopic,  crystalline  mass,  easily  soluble  in  water 
in  alcohol. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  3  gm.  of  ammonium  acetate,  when  ignited,  should 
leave  no  weighable  residue.  (Indicating  less  than  0.0167  per  cent.) 

Chlorides.  —  The  solution  of  1  gm.  of  ammonium  acetate  in  20  c.c.  of  water, 
acidulated  with  5  c.c.  of  nitric  acid,  should  show  no  change  on  the  addition 
of  silver  nitrate  solution.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Sulphates.  —  On  adding  1  c.c.  of  hydrochloric  acid  to  a  solution  of  1  gm. 
of  ammonium  acetate  in  20  c.c.  of  water,  followed  by  barium  chloride  solution, 
no  precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indi- 
cating less  than  0.0075  per  cent  SO3.) 

Heavy  Metals  and  Earths.  —  The  solution  of  5  gm.  of  ammonium  acetate 
in  100  c.c.  of  water  should  not  be  affected  by  hydrogen  sulphide  water.  Fur- 
thermore, the  addition  of  ammonia  water  and  ammonium  oxalate  solution  should 
cause  neither  a  coloration  nor  a  turbidity.  (Indicating  no  heavy  rrctals  present, 
and  less  than  0.004  per  cent  earths  as  Ca.) 


AMMONIUM   CARBONATE 
(NH4)HCO3-  (NH4)NH2CO2 

The  term  "  ammonium  carbonate  "  is  generally  applied  to  a 
mixture  of  ammonium  bicarbonate  and  carbamate,  forming  a  crys- 
talline, white,  translucent  mass  which  readily  effloresces,  becomes 
opaque,  and  gives  off  an  odor  of  ammonia. 

Ammonium  carbonate  is  soluble  in  5  parts  of  water,  and  con- 
tains at  least  31.76  per  cent  of  ammonia  (NHs). 

TESTS   OF  PURITY 

Non-  volatile  Matter.  —  5  gm.  of  ammonium  carbonate,  when  ignited,  should 
leave  no  weighable  residue.  (Indicating  less  than  0.01  per  cent.) 

Calcium.  —  The  solution  of  2  gm.  of  ammonium  carbonate  in  20  c.c.  of 
water  and  10  c.c.  of  acetic  acid  (sp.gr.  1.040-1.042)  should  remain  clear  ten 
minutes  after  the  addition  of  ammonium  oxalate  solution.  (Indicating  less 
than  0.0125  per  cent  Ca.) 

Sulphates.  —  Dissolve  5  gm.  of  ammonium  carbonate  in  100  c.c.  of  water 
and  10  c.c.  of  hydrochloric  acid,  heat  the  solution  to  boiling,  and  add  barium 
chloride  solution.  No  precipitate  of  barium  sulphate  should  form  on  standing 
fifteen  hours.  (Indicating  less  than  0.01  per  cent  SOa.) 

Chlorides  and  Thiosulphates.  —  The  solution  of  2  gm.  of  ammonium  carbonate 
in  20  c.c.  of  water  should  not  be  affected  on  adding  10  c.c.  of  nitric  acid,  followed 
by  silver  nitrate  solution.  (Indicating  less  than  0.00025  per  cent  Cl,  and  less 
than  0.0008  per  cent 


AMMONIUM   CHLORIDE  39 


Phosphate.  —  A  solution  of  2  gm.  of  ammonium  carbonate  in  20  c.c.  of 
water  and  10  c.c.  of  nitric  acid  must  show  no  yellow  precipitate  within  fifteen 
minutes  after  the  addition  of  20  c.c.  of  ammonium  molybdate  solution,  keeping 
the  temperature  about  40°  C.  (Indicating  less  than  0.01  per  cent  P2O5.) 

Heavy  Metals.  —  To  a  solution  of  2  gm.  of  ammonium  carbonate  in  20  c.c. 
of  water  are  added  a  few  drops  of  ammonium  sulphide  solution.  Neither  a  green 
nor  a  brown  color  should  appear.  (Indicating  none  present.) 

No  change  should  appear  upon  adding  hydrogen  sulphide  water  to  a  solution 
of  2  gm.  of  ammonium  carbonate  in  20  c.c.  of  water  containing  10  c.c.  of  hydro- 
chloric acid.  (Indicating  none  present.) 

Sulphocyanates.  —  The  solution  of  1  gm.  of  ammonium  carbonate  in  20 
c.c.  of  water  and  3  c.c.  of  hydrochloric  acid  should  not  be  reddened  on  adding 
1  drop  of  ferric  chloride  solution.  (Indicating  less  than  0.12  per  cent  CNS.) 

Tar  Bases  (Aniline,  etc.).  —  Acidify  1  gm.  of  ammonium  carbonate  with  5 
c.c.  of  nitric  acid,  and  evaporate  the  solution  to  dryness  on  the  water-bath. 
The  residue  must  have  a  pure  white  color.  (Indicating  none  present.) 

Quantitative  Determination.  —  Dissolve  2  gm.  of  ammonium  carbonate 
(translucent  undecomposed  pieces)  in  50  c.c.  of  water  mixed  with  50  c.c.  of 
normal  hydrochloric  acid.  Then  titrate  the  excess  of  acid  with  normal  potassium 
hydroxide  solution,  using  methyl  orange  as  indicator.  At  least  37.3  c.c.  of  the 
acid  should  be  consumed  by  the  carbonate. 

1  c.c.  of  normal  HC1 =0.01703  gm.  of  NH3,  log.  23121. 

AMMONIUM  CHLORIDE 
NH4C1.    Mol.  Wt.  53.50 

A  white,  crystalline  powder,  soluble  in  3  parts  of  water,  and 
in  60  parts  of  alcohol. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  5  gm.  of  ammonium  chloride,  when  gently  ignited, 
should  leave  no  weighable  residue.  (Indicating  less  than  0.01  per  cent.) 

Phosphates  and  Arsenates.  —  Dissolve  5  gm.  of  ammonium  chloride  in  20 
c.c.  of  water,  and  add  to  the  clear  solution  3  c.c.  of  magnesia  mixture*  and  10 
c.c.  of  ammonia  water.  No  precipitate  should  form  on  standing  fifteen  hours. 
(Indicating  less  than  0.001  per  cent  P2Of.,  and  less  than  0.005  per  cent  As2O5.) 

Heavy  Metals.  —  The  solution  of  2  gm.  of  ammonium  chloride  in  20  c.c. 
of  water  must  remain  clear  after  the  addition  of  ammonia  water,  and  must  show 
neither  a  green  nor  a  brown  color  upon  the  further  addition  of  ammonium  sul- 
phide solution.  (Indicating  none  present.) 

The  solution  of  2  gm.  of  ammonium  chloride  in  20  c.c.  of  water  must  show 
no  change  upon  the  addition  of  a  few  drops  of  hydrochloric  acid  and  some  hydrogen 
sulphide  water.  (Indicating  none  present.) 

Sulphates.  —  The  solution  of  5  gm.  of  ammonium  chloride  in  100  c.c.  of 
water  with  5  c.c.  of  hydrochloric  acid  and  some  barium  chloride  solution  should 
show  no  precipitate  of  barium  sulphate  on  standing  fifteen  hours.  (Indicating 
less  than  0.005  per  cent  SO3.) 

Sulphocyanates.  —  Dissolve  1  gm.  of  ammonium  chloride  in  20  c.c.  of  water, 
and  add  to  the  solution  2  c.c.  of  hydrochloric  acid  and  1  drop  of  ferric  chloride 
solution.  The  liquid  should  not  acquire  a  red  color.  (Indicating  less  than 
0.12  per  cent  CNS.) 


*  See  note  under  Acid  Hydrobromic  (page  9)  for  formula'. 


4Q  CHEMICAL  REAGENTS 


Tar  Bases  (Aniline,  etc.)  —  On  evaporating  to  dryness  1  gm.  of  ammonium 
chloride  with  5  c.c.  of  nitric  acid  on  the  water-bath,  the  residue  must  have  a 
pure  white  color.  (Indicating  none  present.) 

Calcium.  —  2  gm.  of  ammonium  chloride  are  dissolved  in  20  c.c.  of  water. 
When  1  c.c.  of  ammonia  water  and  some  ammonium  oxalate  solution  are  added 
the  mixture  must  remain  clear  ten  minutes.  (Indicating  less  than  0.01  per  cent  Ca.; 


AMMONIUM   CHROMATE 
(Ammonium  Chromate,  Neutral) 

(NH4)2CrO4.     Mol.  Wt.  152.08 
Yellow,  needle-shaped  crystals  soluble  in  5  parts  of  cold  water. 

TESTS   OF  PURITY 

Alkalies.  —  Add  50  c.c.  of  solution  of  lead  acetate  (1  :  10  and  free  from 
alkalies)  to  a  solution  of  2  gm.  of  ammonium  chromate  in  100  c.c.  of  water. 
Filter  off  the  precipitate  of  lead  chromate,  and  remove  the  lead  from  the  filtrate 
by  passing  hydrogen  sulphide  gas  through  it.  Filter,  and  evaporate  this  (lead- 
free)  filtrate  to  dryness.  The  residue  thus  obtained  should  not  weigh  more  than 
0.005  gm.  after  ignition.  (Indicating  not  more  than  0.25  per  cent.) 

Chlorides.  —  Add  10  c.c.  of  nitric  acid  to  a  solution  of  1  gm.  of  ammonium 
chromate  in  20  c.c.  of  water  and  warm  to  about  50°  C.  The  addition  of  a  few 
drops  of  solution  of  silver  nitrate  to  this  should  produce  neither  a  turbidity  nor 
a  precipitate  within  five  minutes.  (Indicating  less  than  0.0025  per  cent  Cl.) 

Sulphates.  —  The  addition  of  solution  of  barium  chloride  to  a  solution  of  3 
gm.  of  ammonium  chromate  in  100  c.c.  of  water  and  30  c.c.  of  hydrochloric  acid 
should  cause  no  precipitate  of  barium  sulphate  within  fifteen  hours.  (Indicating 
less  than  0.029  per  cent  SOa.) 

Aluminum  and  Calcium.  —  The  solution  of  2  gm.  of  ammonium  chromate  in 
30  c.c.  of  water  upon  the  addition  of  5  c.c.  of  ammonia  water  and  some  solution 
of  ammonium  oxalate  should  contain  no  precipitate  at  the  end  of  fifteen  hours. 
(Indicating  less  than  0.1  per  cent  Al  and  less  than  0.005  per  cent  Ca.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ammonium  chromate  in 
sufficient  water  to  make  100  c.c.  of  solution,  and  of  this  place  10  c.c.  in  a  glass- 
stoppered  flask  of  about  400  c.c.  capacity.  Add  2  gm.  of  potassium  iodide,  5 
c.c.  of  diluted  sulphuric  acid  (sp.gr.  1.110-1.114),  and  350  c.c.  of  water.  Titrate 
the  liberated  iodine  with  decinormal  solution  of  sodium  thiosulphate,  using  starch 
solution  as  indicator. 

1  c.c.  of  decinormal  solution  of  Na2S2O3  =  0.0050695  gm.  of  (NH4)2CrO4,  log. 
70497. 

AMMONIUM   CITRATE   SOLUTION 

A  clear,  colorless  liquid,  containing  150  gm.  of  pure,  crystallized 
citric  acid  and  23  gm.  of  ammonia-nitrogen  (  =  27.96  gm.  of  NH3) 
per  liter.  The  solution  has  an  acid  reaction  to  litmus  paper,  and 
is  used  for  determining  citrate-soluble  phosphoric  acid  in  Thomas 
slag,  by  the  method  of  Wagner. 


AMMONIUM  DITHIOCARBONATE  SOLUTION  41 


TEST  FOR  PROPER  CONTENT  OF  AMMONIA-NITROGEN 

Dilute  25  c.c.  of  the  ammonium  citrate  solution  with  water  to  250  c.c.  To 
25  c.c.  of  this  diluted  solution  add  3  gm.  of  calcined  magnesia  and  about  200 
c.c.  of  water,  and  distil,  using  a  receiver  containing  40  c.c.  of  semi-normal  sul- 
phuric acid.  After  the  distillation  titrate  the  excess  of  acid  with  semi-normal 
potassium  hydroxide  solution,  using  methyl  orange  as  indicator. 

1  c.c.  of  semi-normal  H2SO4=0.00705  gm.  of  N,  log.  84541,  =0.008517  gm. 
of  NH3,  log.  93029. 

AMMONIUM  DITHIOCARBONATE  SOLUTION 

CO(SNH4)2.    Mol.  Wt.  128.22 

A  yellow  liquid  of  ammoniacal  odor,  and  containing  about  10  to 
12  per  cent  of  ammonium  dithiocarbonate,  about  8  per  cent  cf 
ammonium  chloride,  and  small  quantities  of  ammonium,  sulphocy- 
anate  and  ammonium  sulphide.  It  is  used  as  a  substitute  for 
hydrogen  sulphide  and  ammonium  sulphide. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  10  c.c.  of  ammonium  dithiocarbonate  solution,  on 
being  evaporated  and  ignited,  should  leave  no  weighable  residue.  (Indicating 
less  than  0.005  per  cent.) 

Ammonium  Carbonate.  —  On  adding  3  c.c.  of  calcium  chloride  solution  to 
10  c.c.  of  the  ammonium  dithiocarbonate  solution,  no  precipitate  should  form, 
even  on  warming.  (Indicating  less  than  0.0045  per  cent  [NH^COs.) 

NOTE.  —  Regarding   the   employment   of   ammonium   dithiocarbonate   see 
M.  Vogtherr,  Ber.  d.  pharm.  Ges.,  8,  232  (1898)  [or  Pharm.  Zentralhalle,  39, 
C92  (1898)];  abst.,  J.  Chem.  Soc.,  78,  II,  241  (1900). 

AMMONIUM   FLUORIDE 

NH4F.     Mol.  Wt.  37.04 

White  crystals,  easily  soluble  in  water,  affording  a  solution  which 
usually  exhibits  an  acid  reaction  because  of  the  presence  of  NK^F  •  HF. 
TESTS   OF  PURITY 

Non-volatile  Matter.  —  10  gm.  of  ammonium  fluoride  on  ignition  should 
leave  no  weighable  residue.  (Indicating  less  than  0.005  per  cent.) 

Chlorides.  —  On  dissolving  2  gm.  of  ammonium  fluoride  in  20  c.c.  of  water 
in  a  platinum  dish,  and  adding  a  few  drops  of  nitric  acid,  followed  by  silver 
nitrate  solution,  the  liquid  must  show  at  most  a  slight  opalescence.  (Indicating 
less  than  0.001  per  cent  Cl.)  ^ 

Sulphates  and  Silicofluorides.  —  Dissolve  5  gm.  of  ammonium  fluoride  in  a 
platinum  dish  in  25  c.c.  of  water,  and  add  25  c.c.  of  hydrochloric  acid,  followed 
by  1  to  2  c.c.  barium  chloride  solution.  On  now  mixing  this  solution  with  50 
c.c.  of  alcohol,  no  turbidity  should  ensue.  (Indicating  less  than  0.3  per  cent 
SO3,  and  less  than  0.015%(NH4)2SiF6.) 


42  CHEMICAL  REAGENTS 


Heavy  Metals.  —  Dissolve  2  gm.  of  ammonium  fluoride  in  25  c.c.  of  water, 
in  a  platinum  dish,  add  to  the  solution  a  few  drops  of  hydrochloric  acid  and 
some  hydrogen  sulphide  water.  No  change  should  appear.  (Indicating  none 
present.) 

A  solution  of  2  g  .of  ammonium  fluoride  in  20  c.c.  of  water  in  a  platinum 
dish  is  made  alkaline  with  ammonia  water.  It  should  remain  clear.  The  addition 
to  this  of  a  few  drops  of  ammonium  sulphide  solution  should  produce  at  most 
a  slight  greenish  coloration,  but  a  precipitate  should  not  form.  (Indicating  at 
most  a  trace.) 

AMMONIUM  MOLYBDATE 

(NH4)6Mo7024+4H20.    Mol.  Wt.  1236.32 

Large,  colorless,  or  slightly  greenish  crystals,  very  easily  soluble 
in  water.  When  heated  they  liberate  ammonia  and  water,  leaving 

molybdic  anhydride. 

TESTS   OF  PURITY 

Phosphates.  — 10  gm.  of  ammonium  molybdate  with  25  c.c.  of  water  and 
20  c.c.  of  ammonia  water  (sp.gr.  0.92)  should  afford  a  clear  solution.  Add  this 
solution  to  150  c.c.  of  nitric  acid  (sp.gr.  1.20)*.  No  yellow  precipitate  should 
form  on  standing  fifteen  hours  at  a  temperature  of  about  40°  C.  (Indicating 
less  than  0.0005  per  cent  P2O5.) 

Heavy  Metals.  —  Dissolve  2  gm.  of  ammonium  molybdate  in  5  c.c.  of  water 
and  5  c.c.  of  ammonia  water,  and  to  the  solution  add  a  few  drops  of  ammonium 
sulphide  solution.  No  green  coloration  should  develop,  nor  should  a  precipitate 
form.  (Indicating  none  present.) 

Sulphates.  —  On  dissolving  1  gm.  of  ammonium  molybdate  in  10  c.c.  of  water, 
and  acidifying  the  solution  "with  5  c.c.  of  nitric  acid,*  no  change  should  be  observed 
on  the  further  addition  of  barium  nitrate  solution.  (Indicating  less  than  0.175 
per  cent  SO3.) 

Chlorides.  —  2  gm.  of  ammonium  molybdate  dissolved  in  10  c.c.  of  water 
and  acidulated  with  10  c.c.  of  nitric  acid*  should  show  at  most  a  slight  opal- 
escence  upon  the  addition  of  silver  nitrate  solution.  (Indicating  less  than 
0.001  per  cent  Cl.) 

Nitrate.  —  To  a  solution  of  1  gm.  of  ammonium  molybdate  and  a  small 
crystal  of  sodium  chloride  in  10  c.c.  of  water  are  added  1  drop  of  a  solution  of 
indigo  (1  :  1000)  and  10  c.c.  of  sulphuric  acid  (sp.gr.  1.84).  The  blue  color 
of  the  solution  must  not  disappear  upon  mixing  the  liquids.  (Indicating  less 
than  0.0032  per  cent  N2O5.) 

Quantitative  Determination.  —  The  content  of  molybdic  anhydride  may  be 
approximately  determined  by  gently  igniting  about  1  gm.  of  the  salt  until  the 
ammoniacal  odor  has  disappeared,  and  then  weighing  the  residue  of  molybdic 
anhydride;  it  should  amount  to  about  81  per  cent.  The  accurate  determination 
is  carried  out  in  the  manner  described  under  Acid  Molybdic  Anhydride,  on  page  14. 

AMMONIUM  MOLYBDATE  SOLUTION 

This  solution,  known  as  solution  of  acid  molybdic  according  to 
Fresenius,  is  made  by  dissolving  150  gm.  of  ammonium  molybdate 


*  The  ammonium  molybdate  solution  should  be  added  to  the  nitric  acid 
gradually  and  with  constant  rotation;  never  otherwise. 


AMMONIUM  NITRATE  43 

in  1  liter  of  water,  gently  heating,  and  subsequently  pouring  the 
resulting  liquid,  with  constant  stirring,  into  1  liter  of  nitric  acid 
(sp.gr.  1.20). 

AMMONIUM  NITRATE 

NHJfOs.    Mol.  Wt.  80.05 

Colorless  crystals  very  easily  soluble  in  water. 
TESTS  OF  PURITY 

The  tests  to  be  made  and  conditions  to  be  observed  are  those  described 
under  Ammonium  Chloride;  and,  in  addition,  the  following  tests  for  chlorides 
and  nitrites: 

Chlorides.  —  On  dissolving  2  gm.  of  ammonium  nitrate  in  20  c.c.  of  water, 
and  adding  a  few  drops  of  nitric  acid,  followed  by  silver  nitrate  solution,  the 
liquid  should  remain  unchanged.  (Indicating  less  than  0.00025  per  cent  Cl.) 

Nitrites.  —  To  the  solution  of  1  gm.  of  ammonium  nitrate  in  20  c.c.  of  water 
are  added  1  c.c.  of  16  per  cent  sulphuric  acid  and  1  c.c.  of  a  freshly  prepared 
(1  :  100)  colorless*  solution  of  metaphenylenediamine  hydrochloride;  no  yellow 
or  yellowish-brown  color  should  develop.  (Indicating  less  than  0.00055  per  cent 
N203.) 

AMMONIUM   OXALATE 
(NH4)2C2O4+H2O.    Mol.  Wt.  142.10 
Colorless  crystals,  clearly  soluble  in  25  parts  of  cold  water. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  3  gm.  of  ammonium  oxalate  on  ignition  should  leave 
no  weighable  residue.  (Indicating  less  than  0.017  per  cent.) 

Sulphates.  —  Dissolve  5  gm.  of  ammonium  oxalate  in  200  c.c.  of  water,  heat 
the  solution  to  boiling,  and  then  add  10  c.c.  of  hydrochloric  acid,  followed  by 
barium  chloride  solution.  No  precipitate  of  barium  sulphate  should  form  on 
standing  fifteen  hours.  (Indicating  less  than  0.005  per  cent  SO3.) 

Chlorides.  —  On  adding  to  a  solution  of  1  gm.  of  ammonium  oxalate  in  25 
c.c.  of  water,  10  c.c.  of  nitric  acid,  and  a  few  drops  of  silver  nitrate  solution, 
at  most  a  slight  opalescence  should  develop  on  shaking.  (Indicating  less  than 
0.0025  per  cent  Cl.) 

Heavy  Metals.  —  To  a  solution  of  1  gm.  of  ammonium  oxalate  in  25  c.c. 
of  water,  add  hydrogen  sulphide  water;  the  solution  should  remain  unchanged. 
Now  add  to  the  liquid  5  c.c.  of  ammonia  water;  no  green  color  should  develop, 
nor  should  a  precipitate  form.  (Indicating  none  present.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ammonium  oxalate  in  100 
c.c.  of  water.  To  25  c.c.  of  this  solution  add  6  to  8  c.c.  of  sulphuric  acid  (sp.gr. 
1.84),  warm  to  about  60°  C.,  and  titrate  with  decinormai  potassium  permanganate 
solution. 

1  c.c.  of  decinormai  KMnO.i  =  0.007105  gm.  of  (NH4)2C2O4+H2O,  log.  85156. 

*  Should  the  solution  of  metaphenylenediamine  hydrochloride  already  have 
a  color  it  is  to  be  decolorized  before  use  by  warming  with  ignited  animal  charcoal. 


44  CHEMICAL  REAGENTS 

• 

AMMONIUM  PERSULPHATE 

(NH4)2S2O8.    Mol.  Wt.  228.22 

Colorless  crystals,  which  dissolve  very  easily  in  water  with  the 
formation  of  a  solution  acid  to  litmus  paper.  The  preparation  con- 
tains at  least  95  per  cent  of  (NH4)2S20g,  although  gradual  deteri- 
oration occurs,  oxygen  being  liberated. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  Ignition  of  3  gm.  of  ammonium  persulphate  should 
leave  a  residue  not  exceeding  0.002  gm.  (Indicating  not  more  than  0.0667  per 
cent.) 

Chlorides.  —  The  addition  of  3  to  5  drops*  of  solution  of  silver  nitrate  to  a 
solution  of  1  gm.  of  ammonium  persulphate  in  20  c.c.  of  water  should  cause  at 
most  a  slight  opalescence.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  Evaporate  to  dryness  on  the  water-bath  a  solution  of  4 
gm.  of  ammonium  persulphate  in  50  c.c.  of  sulphurous  acid  (sp.gr.  1.029-1.035), 
and  dissolve  the  residue  thus  obtained  in  40  c.c.  of  water. 

Hydrogen  sulphide  water  should  produce  no  visible  change  in  20  c.c.  of  this 
solution.  (Indicating  none  present.) 

Ammonia  water  added  in  excess  to  the  other  20  c.c.  of  the  above  solution  of 
the  residue  from  the  evaporation  should  cause  no  visible  change;  and  the  sub- 
sequent addition  of  a  few  drops  of  solution  of  ammonium  sulphide  should  produce 
at  most  a  green  color,  in  no  case  a  precipitate.  (Indicating  at  most  a  trace.) 

Quantitative  Determination.  —  In  a  graduated  100  c.c.  flask  place  1  gm.  of 
ammonium  persulphate  and  pour  over  it  a  solution  of  5  gm.  of  potassium  iodide 
in  50  c.c.  of  water,  followed  by  10  c.c.  of  diluted  sulphuric  acid  (sp.gr.  1.110-1.114). 
Allow  the  mixture  to  stand  with  frequent  shaking  for  about  half  an  hour,  then 
fill  to  the  mark,  mix,  and  titrate  20  c.c.  of  it  with  decinormal  solution  of  sodium 
thiosulphate. 

1  c.c.  of  decinormal  Na2S2O3  =  0.01  1411  gm.  of  (NH^SaOs,  log.  05732. 


AMMONIUM   PHOSPHATE 

(Secondary  Ammonium  Phosphate) 

(NH4)2HPO4.    Mol.  Wt.  132.13 

Colorless  crystals,  or  white,  crystalline  powder,  soluble  in  4 
parts  of  cold,  or  0.5  part  of  boiling,  water.  The  aqueous  solution 
is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Alkalies.  —  The  solution  of  2  gm.  of  ammonium  phosphate  in  100  c.c.  of 
water  is  treated  with  lead  acetate  solution  f  in  slight  excess  to  precipitate  the 


*  Larger  quantities  of  the  silver  nitrate  solution  obscure  the  chloride  reaction 
by  a  black  precipitate. 

f  Must  be  free  from  alkalies,  etc. 


AMMONIUM  SULPHATE  45 


phosphoric  acid,  and  is  then  filtered.  The  excess  of  lead  in  the  nitrate  is  then 
precipitated  with  hydrogen  sulphide,  the  liquid  filtered,  the  filtrate  evaporated 
to  dry  ness,  and  the  residue  ignited.  The  residue  should  not  weigh  more  than 
0.003  gm.  (indicating  not  more  than  0.15  per  cent),  nor  should  it  have  an  alkaline 
reaction  to  litmus  paper  after  moistening  with  a  few  drops  of  water. 

Arsenic.  —  On  shaking  1  gm.  of  powdered  ammonium  phosphate  with  3  c.c. 
of  stannous  chloride  solution,  the  mixture  should  not  darken  within  one  hour. 
(Indicating  less  than  0.0015  per  cent  As.) 

Carbonates  and  Sulphates.  —  On  adding  hydrochloric  acid  to  a  solution  of 
1  gm.  of  ammonium  phosphate  in  20  c.c.  of  water,  no  effervescence  should  take 
place  (indicating  less  than  2.0  per  cent  CO2);  and  on  adding  barium  chloride 
solution,  no  precipitate  of  barium  sulphate  should  form  on  standing  fifteen 
hours.  (Indicating  less  than  0.0075  per  cent  SO3.) 

Chlorides.  —  On  dissolving  1  gm.  of  ammonium  phosphate  in  20  c.c.  of  water, 
and  adding  5  c.c.  of  nitric  acid,  followed  by  silver  nitrate  solution,  not  more 
than  a  very  slight  opalescerce  should  develop.  (Indicating  less  than  0.0015 
per  cent  Cl.) 

Nitrates.  —  Dissolve  2  gm.  of  ammonium  phosphate  and  a  small  crystal  of 
sodium  chloride  in  10  c.c.  of  water,  and  to  the  solution  add  1  drop  of  indigo 
solution  (1  :  1000),  followed  by  10  c.c.  of  concentrated  sulphuric  acid.  The 
liquid  should  still  retain  its  blue  color  upon  shaking.  (Indicating  less  than 
0.0016  per  cent  N2O5.) 

Heavy  Metals.  —  On  dissolving  2  gm.  of  ammonium  phosphate  in  20  c.c. 
of  water,  acidifying  the  solution  with  hydrochloric  acid,  and  then  adding  hydrogen 
sulphide  water,  no  change  should  be  seen.  Upon  dissolving  2  gm.  of  ammonium 
pho-phate  in  20  c.c.  of  water  and  adding  ammonium  sulphide  solution,  no  green 
color  should  develop,  nor  should  a  precipitate  form.  (Indicating  none  present.) 

Quantitative  Determination.  —  1  gm.  of  ammonium  phosphate  is  dis  olved 
in  100  c.c.  of  water  and  titrated  with  normal  hydrochloric  acid,  using  methyl 
orange  as  indicator. 

1  c.c.  of  normal  HC1  =  0.13213  gm.  of  (NH4)2HPO4,  log.  12100. 

AMMONIUM   SULPHATE 

(NH4)2SO4.     Mol.  Wt.  132.15 

Colorless  crystals,  soluble  in  2  parts  of  cold,  and  in  1  part  of 
boiling,  water;  insoluble  in  alcohol. 

TESTS   OF  PURITY 

Non- volatile  Matter.  —  3  gm.  of  ammonium  sulphate  on  ignition  should  leave 
no  weighable  residue.  (Indicating  less  than  0.017  per  cent.) 

Chlorides.  —  The  solution  of  2  gm.  of  ammonium  sulphate  in  20  c.c.  of  water 
should  show  no  change  on  acidifying  with  nitric  acid  and  then  adding  silver 
nitrate  solution.  (Indicating  less  than  0.00025  per  cent  Cl.) 

Heavy  Metals.  —  The  solution  of  2  gm.  of  ammonium  sulphate  in  20  c.c. 
of  water  should  remain  unaffected  after  acidulating  with  hydrochloric  acid  and 
adding  hydrogen  sulphide  water.  (Indicating  none  present.) 

The  solution  of  2  gm.  of  ammonium  sulphate  in  20  c.c.  of  water  should  remain 
clear  upon  the  addition  of  ammonia  water,  and  upon  the  further  addition  of 
ammonium  sulphide  solution  neither  a  green  nor  a  brown  color  should  appear, 
nor  should  a  precipitate  form.  (Indicating  none  present.) 

Sulphocyanates.  —  Dissolve  1  gm.  of  ammonium  sulphate  in  20  c.c.  of  water; 
on  adding  to  the  solution  2  c.c.  of  hydrochloric  acid  and  1  drop  of  ferric  chloride 


46  CHEMICAL  REAGENTS 


solution,  the  liquid  should  not  acquire  a  red  color.  (Indicating  less  than  0.12 
per  cent  CNS.) 

Phosphates  and  Arsenates.  —  Dissolve  5  gm.  of  ammonium  sulphate  in  20 
c.c.  of  water,  and  add  to  the  clear  solution  3  c.c.  of  magnesia  mixture*  and  10 
c.c.  of  ammonia  water.  No  precipitate  should  form  on  standing  fifteen  hours. 
(Indicating  less  than  0.001  per  cent  P2O5,  and  less  than  0.005  per  cent  As2O6.) 

Nitrates.  —  Dissolve  2  gm.  of  ammonium  sulphate  and  a  small  crystal  of 
sodium  chloride  in  10  c.c.  of  water,  and  add  to  the  solution  1  drop  of  indigo 
solution  (1  :  1000),  followed  by  10  c.c.  of  concentrated  sulphuric  acid.  The 
liquid  should  retain  its  blue  color  upon  shaking.  (Indicating  less  than  0.0016 
per  cent  NaOs.) 

AMMONIUM   SULPHIDE  SOLUTION 

(Ammonium  Sulphydrate  Solution) 

A  colorless  or  yellowish  liquid,  produced  by  passing  hydrogen 
sulphide  into  ammonia  water.  It  is  strongly  alkaline  towards 
litmus  paper. 

TESTS  OF  PURITY 

Arsenic,  Antimony  and  Tin.  —  On  adding  hydrochloric  acid  to  50  c.c.  of 
ammonium  sulphide  solution  to  acidity,  hydrogen  sulphide  gas  is  liberated  in 
copious  amounts,  but  no  colored  precipitate  should  form.  (Indicating  less  than 
0.006  per  cent  As,  0.0007  per  cent  Sb,  or  0.0013  per  cent  Sn.) 

Non-volatile  Matter.  —  On  evaporating  and  igniting  10  c.c.  of  ammonium 
sulphide  solution  in  a  porcelain  dish,  no  weighable  residue  should  remain.  (Indi- 
cating less  than  0.005  per  cent.) 

Ammonium  Carbonate.  —  On  adding  3  c.c.  of  calcium  chloride  solution  to 
10  c.c.  of  ammonium  sulphide  solution,  no  precipitate  should  form,  even  on 
warming.  (Indicating  less  than  0.005  per  cent  CO2.) 

Chloride. —  To  20  c.c.  of  the  filtrate  obtained  in  the  Quantitative  Determina- 
tion of  Sulphidic  Sulphur  (see  the  following  test)  add  nitric  acid  to  acid  reaction. 
No  turbidity  or  precipitation  should  result.  (Indicating  less  than  0.005  per 
cent  Cl.) 

Quantitative  Determination  of  the  Sulphidic  Sulphur.  —  Dilute  10  gm.  of 
ammonium  sulphide  solution  to  100  c.c.,  place  5  c.c.  of  this  dilution  in  a  graduated 
flask  of  100  c.c.  capacity,  add  20  c.c.  of  ammonia  water  and  50  c.c.  of  decinormal 
solution  of  silver  nitrate,  fill  with  water  to  the  mark,  mix  the  contents  of  the  flask 
thoroughly,  and  filter.  Mix  50  c.c.  of  the  filtrate  with  20  c.c.  of  nitric  acid,  and 
after  adding  5  c.c.  of  cold  saturated  solution  of  ferric  ammonium  sulphate, 
titrate  with  decinormal  solution  of  ammonium  sulphocyanate. 

1  c.c.  decinormal  AgNO3  =  0.0016035  gm.  S,  log.  20506. 

Quantitative  Determination  of  the  Ammonia.  —  Dilute  20  gm.  of  the  ammo- 
nium sulphide  solution  to  500  c.c.  To  50  c.c.  of  this  dilution  add  30  c.c.  of 
Sodium  Hydroxide  Solution,  Solution  I,  Free  from  Nitrogen,  and  distil  about 
50  c.c.,  collecting  the  distillate  in  a  receiver  containing  20  c.c.  of  normal  hydro- 
chloric acid  solution.  Titrate  the  distillate  with  normal  solution  of  potassium 
hydroxide,  using  methyl  orange  as  indicator. 

1  c.c.  normal  HC1  =  0.01703  gm.  NH3,  log.  23121. 


*  See  note  under  Acid  Hydrobromic  (page  9)  for  formula. 


AMMONIUM  SULPHOCYANATE  47 

AMMONIUM  SULPHOCYANATE 

(Ammonium  Thiocyanate) 
NH4SCN.    Mol.  Wt.  76.12 

Colorless  crystals,  easily  soluble  in  water  and  in  alcohol. 

TESTS  OF  PURITY 

Non-volatile  Matter.  —  2  gm.  of  ammonium  sulphocyanate,  on  being  ignited, 
should  leave  no  weighable  residue.  (Indicating  less  than  0.025  per  cent.) 

Substances  Insoluble  in  Alcohol.  —  1  gm.  of  ammonium  sulphocyanate 
should  completely  dissolve  in  10  c.c.  of  absolute  alcohol,  and  yield  a  perfectly 
clear  solution.  (Indicating  none  present.) 

Sulphates.  —  On  adding  a  few  drops  of  hydrochloric  acid,  followed  by  barium 
chloride  solution,  to  a  solution  of  1  gm.  of  ammonium  sulphocyanate  in  20  c.c. 
of  water,  no  reaction  should  be  observed  within  five  minutes.  (Indicating 
less  than  0.01  per  cent  SO3.) 

Heavy  Metals.  —  On  dissolving  1  gm.  of  ammonium  sulphocyanate  in  20 
c.c.  of  water,  and  adding  to  the  solution  several  drops  of  ammonium  sulphide 
solution,  no  precipitate  should  form,  nor  should  a  brown  or  green  color  develop. 
(Indicating  none  present.) 

Iron.  —  The  solution  of  1  gm.  of  ammonium  sulphocyanate  in  20  c.c.  of 
water  should  remain  perfectly  colorless  on  adding  a  few  drops  of  hydrochloric 
acid.  (Indicating  less  than  0.0004  per  cent  Fe.) 

AMMONIUM  THIOACETATE  SOLUTION 

(Schiff's  Reagent) 
CH3COSNH4.    Mol.  Wt.  93.14 

A  clear,  yellowish  liquid,  having  a  faint  odor  resembling  that 
of  ammonium  sulphide,  and  slightly  alkaline  to  litmus  paper.  The 
solution  contains  about  30  per  cent  of  ammonium  thioacetate. 

TESTS  OF  PURITY 

Non-volatile  Matter.  — 10  c.c.  of  ammonium  thioacetate  solution  on  evapo- 
ration and  ignition  should  leave  no  weighable  residue.  (Indicating  less  than 
0.005  per  cent.) 

Ammonium  Carbonate.  —  On  adding  3  c.c.  of  calcium  chloride  solution  to 
10  c.c.  of  ammonium  thioacetate  solution,  no  precipitate  should  form,  even  on 
warming.  (Indicating  less  than  0.003  per  cent  [NH4]2CO3.) 

Sulphates.  —  A  mixture  of  10  c.c.  of  ammonium  thioacetate  solution  with 
10  c.c.  of  diluted  acetic  acid  should  not  immediately  be  rendered  turbid  on  the 
addition  of  barium  chloride  solution.  (Indicating  less  than  0.0002  per  cent  SO3.) 

NOTE.  —  The  reagent  can  be  kept  only  a  short  time  unchanged;  it  readily 
becomes  turbid.  It  is,  therefore,  advantageous  to  prepare  only  sufficient  for 
eight  to  ten  days'  use,  which  may  be  done  by  dissolving  the  thioacetic  acid 
in  a  slight  excess  of  ammonia  water. 

Regarding  the  use  of  ammonium  thioacetate  solution  in  analysis,  see  R. 


48  CHEMICAL  REAGENTS 


Schiff  and  N.  P.  Tarugi,  Ber.,  27,  3437  (1894)  [or  Z.  anal.  Chem.,  34,  456  (1895)]; 
abst.,  J.  Chem.  Soc.,  68,  II,  84  (1895).  R.  Schiff,  Ber.,  28,  1204  (1895);  abst., 
J.  Chem.  Soc.,  68,  II,  370  (1895). 


ANILINE 
C6H5NH2.     Mol.  Wt.  93-07 

A  colorless,  oily,  strongly  refractive  liquid,  which  rapidly  becomes 
brown  on  exposure  to  light  and  air. 

Aniline  is  soluble  in  about  35  parts  of  water.  It  solidifies  in  a 
freezing  mixture,  and  then  melts  at  —  8°  C.  Its  specific  gravity 
is  1.027;  its  boiling-point,  183°  C. 

TEST  OF  PURITY 

Hydrocarbons  and  Nitrobenzene.  —  5  c.c.  of  aniline  dissolved  in  10  c.c.  of 
hydrochloric  acid  should  form  a  clear  fluid  which,  on  being  diluted  with  15  c.c. 
of  water,  should  not  become  cloudy  on  cooling.  (Indicating  none  present.) 

NOTE.  —  Regarding  the  examination  of  aniline,  see  Lunge,  Chem.-tech. 
Untersuch.-Meth.,  5  ed.,  3,  886,  890  (1905);  compare  Watt's  Diet,  of  Chem., 
1,  271  (1894).  G.  Schultz,  Chemie  des  Steinkohlenteers,  1,  289  (1886);  com- 
pare Thorpe's  Diet,  of  Appld.  Chem.,  2  ed.,  1,  162  (1895). 


ANTIMONY  OXIDE 

(Antimonous  Oxide;  Antimony  Trioxide) 

Sb2O3.     Mol.  Wt.  288.4 

A  white  powder,  insoluble  in  water,  but  soluble  in  hydrochloric 
acid,  tartaric  acid,  alkali  bitartrates,  and  in  solutions  of  potassium 
or  sodium  hydroxide.  Antimony  trioxide  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Arsenic.  —  On  dissolving  1  gm.  of  antimony  trioxide  in  3  c.c.  of  hydrochloric 
acid  (sp.gr.  1.19),  and  adding  3  c.c.  of  stannous  chloride  solution,  the  mixture 
should  not  darken  within  one  hour.  (Indicating  less  than  0.0015  per  cent  As.) 

Foreign  Heavy  Metals.  —  Dissolve  1  gm.  of  antimony  trioxide  with  the  aid 
of  heat  in  30  c.c.  of  sodium  Hydroxide  solution  (sp.gr.  1.3).  Dilute  the  solution 
with  20  c.c.  of  water  and  add  hydrogen  sulphide  water.  Neither  a  white  nor  a 
brownish-black  precipitate  should  form.  (Indicating  none  present.) 

Chlorides.  —  Dissolve  1  gm.  of  antimony  trioxide  with  the  aid  of  heat  in 
30  c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3).  Add  to  the  solution  70  c.c. 
of  nitric  acid,  filter,  and  to  the  filtrate  add  silver  nitrate  solution.  The  liquid 
may  exhibit  at  most  a  slight  turbidity,  but  no  precipitate  should  form.  (Indi- 
cating less  than  0.05  per  cent  Cl.) 


ARSENIC  TRIOXIDE  49 

ARSENIC  TRIOXIDE 

(Arsenous  Acid;  [Acid]  Arsenous  Anhydride) 
As2O3.    Mol.  Wt.  197.92 

White,  vitreous  (amorphous),  or  porcelain-like  crystalline  pieces, 
or  white  powder.  The  amorphous  acid  is  more  easily  and  quickly 
soluble  than  the  crystalline,  but  the  saturated  solution  of  the  former 
is  not  permanent,  the  less  soluble  crystalline  form  being  gradually 
deposited  from  it.  The  crystalline  acid  is  very  slowly  soluble  in 
about  65  parts  of  cold  water,  and  quickly  soluble  in  15  parts  of 

boiling  water. 

TESTS   OF  PURITY 

Non- volatile  Matter.  —  1  gm.  of  arsenic  trioxide  cautiously  heated  in  a 
porcelain  dish  (use  a  hood!)  should  completely  volatilize  and  leave  no  weighable 
residue.  (Indicating  less  than  0.05  per  cent.) 

Barium  Sulphate,  Talcum,  Calcium  Sulphate,  etc.  —  0.5  gm.  of  arsenic 
trioxide  should  be  perfectly  soluble  in  a  mixture  of  5  c.c.  of  ammonia  water  and 
5  c.c.  of  water,  and  should  yield  a  clear  solution.  (Indicating  none  present.) 

Arsenic  Sulphide.  —  Dissolve  5  gm.  of  arsenic  trioxide  in  a  mixture  of  5  c.c. 
of  sodium  hydroxide  solution  and  15  c.c.  of  water;  on  adding  to  the  clear  solution 
2  drops  of  lead  acetate  solution,  no  change  should  appear.  (Indicating  less 
than  0.0005  per  cent  S.) 

Quantitative  Determination.  —  Dissolve*  1  gm.  of  arsenic  trioxide  with  the 
aid  of  6  gm.  of  potassium  bicarbonate  in  50  c.c.  of  boiling  water,  then  allow 
to  cool  to  15°  C.,  and  add  sufficient  water  to  make  the  whole  measure  100  c.c. 
Dilute  10  c.c.  of  this  solution  with  50  c.c.  of  water,  and  titrate  with  decinormal 
iodine  solution. 

1  c.c.  of  decinormal  1  =  0.004948  gm.  of  As2O3,  log.  69443. 

ASBESTOS  PREPARATIONS 
COPPER  OXIDE  ASBESTOS— SILVER  ASBESTOS 

These  two  forms  of  asbestos  are  prepared  according  to  the 
method  of  Pregl,f  and  especially  intended  for  use  in  elementary 
analysis. 


*  It  may  be  quicker  to  dissolve  1  gm.  in  a  freshly  prepared  solution  of  sodium 
hydroxide  (sulphur-free),  slightly  acidulate  with  hydrochloric  acid,  and  then 
add  the  6  gm.  of  bicarbonate.  No  heat  is  necessary  in  this  case.  It  is  always 
quicker  to  use  a  powdered  sample.  Regarding  the  use  of  arsenic  trioxide  in 
analysis  see  Mohr's  Lehrb.  Chem.-anal.  Titriermeth.,  7  ed.,  p.  389  ff.  (1896); 
Button's  Volumetric  Analysis,  10  ed.,  139  (1911). 

t  F.  Pregl,  Ber.,  38,  1434  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  420  (1905). 


50  CHEMICAL  REAGENTS 


AZOLITMIN 

Azolitmin  is  a  particularly  pure,  water-soluble  coloring  matter 
made  from  litmus.  It  occurs  in  the  form  of  blackish-violet  scales. 

Azolitmin  is  used  as  an  indicator,  usually  in  1  per  cent  solution. 
To  make  this,  dissolve  1  gm.  of  azolitmin  in  80  c.c.  of  water  with 
the  aid  of  heat,  then  add  20  c.c.  alcohol  (about  85  per  cent  by 
weight),  and  filter  the  solution  when  cold. 

TEST  OF   SENSITIVENESS 

Add  0.1  c.c.  of  the  above  azolitmin  solution  to  50  «.c.  of  distilled  water, 
free  from  carbon  dioxide.  The  bluish-red  color  of  the  liquid  should  be  changed 
to  red  by  the  addition  of,  at  most,  0.05  c.c.  of  decinormal  hydrochloric  acid, 
and  must  be  changed  to  bluish-violet  by  the  addition  of,  at  most,  0.05  c.c.  of 
decinormal  potassium  hydroxide. 

BARIUM   ACETATE 
Ba(C2H3O2)2+H2O.     Mol.  Wt.  273.43 

A  white,  crystalline  powder,  soluble  in  2  parts  of  water  and  in 
about  100  parts  of  alcohol. 

TESTS  OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  barium  acetate  in  20  c.c.  of  water, 
acidulated  with  5  c.c.  of  nitric  acid,  must  show  at  most  a  slight  opalescence 
on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Calcium  and  Alkalies.  —  Dissolve  5  gm.  of  barium  acetate  in  200  c.c.  of  water, 
add  to  the  solution  2  c.c.  of  hydrochloric  acid,  and  heat  to  boiling.  Now  add 
15  c.c.  of  16  per  cent  sulphuric  acid,  allow  to  stand  fifteen  hours,  filter,  and  mix 
the  filtrate  with  alcohol  (about  85  per  cent  by  weight.)  At  most  a  faint  opal- 
escence should  be  observed;  and  on  evaporating  in  a  platinum  dish  and  igniting, 
not  more  than  0.004  gm.  of  residue  should  remain.  (Indicating  not  more  than  0.08 
per  cent.) 

Heavy  Metals.  —  The  1  :  20  aqueous  solution  should  not  appear  changed  on 
the  addition  of  hydrogen  sulphide  water;  ammonia  water  with  ammonium  sul- 
phide solution  should  produce  no  dark  color  and  no  precipitate.  (Indicating 
none  present.) 

Nitrates.  —  The  blue  color  imparted  by  1  drop  of  1  :  1000  indigo  solution 
to  a  solution  of  1  gm.  of  barium  acetate  and  a  small  crystal  of  sodium  chloride 
in  10  c.c.  of  water  should  not  disappear  on  the  addition  of  10  c.c.  of  concentrated 
sulphuric  acid  followed  by  shaking.  (Indicating  less  than  0.0032  per  cent 


BARIUM   CARBONATE 
BaCO3.    Mol.  Wt.  197.37 

White  pieces  or  powder,  almost  insoluble  in  water  free  from 
carbon  dioxide. 


BARIUM  CHLORIDE  51 


TESTS  OF  PURITY 

Solubility  in  Dilute  Hydrochloric  Acid.  —  5  gm.  of  barium  carbonate  should 
be  completely  soluble  in  10  c.c.  of  hydrochloric  acid  diluted  with  50  c.c.  of  water. 

Barium  Hydroxide.  —  If  1  gm.  of  barium  carbonate  is  shaken  repeatedly 
during  half  an  hour  with  20  c.c.  of  water  free  from  carbon  dioxide,  the  solution 
after  filtering  should  not  be  alkaline,  and  after  evaporation  and  ignition  not  more 
than  0.002  gm.  of  residue  should  remain.  (Indicating  not  more  than  0.223  per  cent 
Ba[OH]2). 

Calcium  and  Alkalies.  —  Dissolve  5  gm.  of  barium  carbonate  in  10  c.c.  of 
hydrochloric  acid  and  200  c.c.  of  water,  and  heat  the  solution  to  boiling.  Then  add 
15  c.c.  of  16  per  cent  sulphuric  acid,  allow  to  stand  fifteen  hours,  filter,  and  mix 
the  filtrate  with  alcohol  (about  85  per  cent  by  weight).  Not  more  than  a  faint 
opalescence  should  be  visible,  and  on  evaporating  in  a  platinum  dish  and  igniting, 
not  more  than  0.003  gm.  of  residue  should  remain.  (Indicating  not  more  than  0.06 
per  cent.) 

Heavy  Metals.  —  Neither  hydrogen  sulphide  water,  nor  ammonia  water 
with  ammonium  sulphide  solution,  should  produce  a  dark  color  or  a  precipitate 
on  being  added  to  a  solution  of  1  gm.  of  barium  carbonate  in  5  c.c.  of  hydro- 
chloric acid  and  15  c.c.  of  water.  The  solution  of  barium  carbonate  in  acid 
and  water  must  be  previously  boiled  to  free  it  from  carbon  dioxide.  (Indicating 
none  present.) 

Chlorides.  —  The  solution  of  1  gm.  of  barium  carbonate  in  5  c.c.  of  nitric 
acid  and  25  c.c.  of  water  should  not  be  affected  by  silver  nitrate  solution. 
(Indicating  less  than  0.0005  per  cent  Cl.) 

Nitrates.  —  The  blue  color  imparted  by  1  drop  of  a  1  :  1000  indigo  solution 
to  the  solution  of  1  gm.  of  barium  carbonate  and  a  small  crystal  of  sodium 
chloride  in  10  c.c.  of  diluted  acetic  acid  should  not  disappear  on  the  addition 
of  10  c.c.  of  concentrated  sulphuric  acid  followed  by  shaking.  (Indicating  less 
than  0.0032  per  cent  N2O5.)  ^ 

Quantitative  Determination.  —  Dissolve  1  gm.  of  barium  carbonate  in  a 
mixture  of  15  c.c.  of  normal  solution  of  hydrochloric  acid  and  50  c.c.  of  water, 
and  titrate  the  solution  with  normal  potassium  hydroxide  solution,  using  methyl 
orange  as  indicator. 

1  c.c.  of  normal  HC1  =  0.098685  gm.  of  BaCO3,  log.  99425. 

BARIUM   CHLORIDE 

.* 

BaCl2+2H2O.    Mol.  Wt.  244.32 

Colorless  crystals,  soluble  in  2.5  parts  of  cold,  and  in  1.5  parts 
of  hot,  water,  and  insoluble  in  absolute  alcohol.  The  aqueous 
solution  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Alkalies.  —  Dissolve  3  gm.  of  barium  chloride  in  100  c.c.  of  water,  add  2 
c.c.  of  hydrochloric  acid  and  heat  to  boiling;  then  add  10  c.c.  of  16  per  cent 
sulphuric  acid,  allow  to  stand  fifteen  hours,  and  filter.  On  evaporating  the  filtrate 
in  a  platinum  dish  and  igniting,  any  residue  remaining  should  weigh  not  more 
than  0.001  gm.  (Indicating  not  more  than  0.0333  per  cent.) 

Strontium  and  Calcium  Chlorides.  —  On  shaking  1  gm.  of  powdered  barium 
chloride  with  20  c.c.  of  absolute  alcohol  five  minutes,  and  then  filtering,  the 
filtrate  on  being  evaporated  and  ignited  should  leave  no  weighable  residue. 
(Indicating  less  than  0,025  per  cent.) 


52  CHEMICAL  REAGENTS 


Heavy  Metals.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should  not  afford  a 
dark  coloration  or  a  precipitate  when  hydrogen  sulphide  water  is  added;  nor 
when  ammonia  water  and  ammonium  sulphide  solution  are  added.  (Indicating 
none  present.) 

Nitrates.  —  On  adding  1  drop  of  a  1  :  1000  indigo  solution  to  a  solution  of 
1  gm.  of  barium  chloride  in  10  c.c.  of  water,  the  blue  color  must  not  disappear 
on  the  addition  of  10  c.c.  of  concentrated  sulphuric  acid  followed  by  shaking. 
(Indicating  less  than  0.0032  per  cent  N2O5.) 

Chlorates.  —  On  warming  2  gm.  of  powdered  barium  chloride  with  10  c.c. 
of  concentrated  hydrochloric  acid  in  a  test-tube,  neither  the  crystals  nor  the 
liquid  should  acquire  a  yellow  color;  nor  should  the  odor  of  chlorine  become 
perceptible.  (Indicating  less  than  0.025  per  cent  C1205.) 

BARIUM  DIOXIDE 

(Barium  Super-  or  Peroxide) 

BaO2.    Mol.  Wt.  169.37 

White,  or  grayish-white  powder,  insoluble  in  water,  but  soluble 
in  cold  hydrochloric  acid  with  the  formation  of  hydrogen  peroxide. 
The  preparation  should  contain  at  least  82  per  cent  of  BaO2. 

TEST  OF   PURITY 

Quantitative  Determination.  —  Introduce  1  gm.  of  barium  peroxide  into  a 
graduated  flask  of  100  c.c.  capacity,  and  add  to  it  5  gm.  of  potassium  iodide 
dissolved  in  30  c.c.  of  water.  Add  10  c.c.  of  hydrochloric  acid,  and  allow  the 
mixture  to  stand  in  the  stoppered  flask  for  about  half  an  hour,  with  frequent 
shaking.  Then  fill  the  flask  to  the  mark,  mix,  and  titrate  10  c.c.  of  the  mixture 
with  decinormal  sodium  thiosulphate  solution,  using  starch  solution  as  the 
indicator.  At  least  9.7  c.c.  of  decinormal  sodium  thiosulphate  should  be  required. 

1  c.c.  of  decinormal  Na2S2O3  =  0.0084685  gm.  of  BaO2,  log.  92780. 

BARIUM   HYDROXIDE 

(Barium  Hydrate) 
Ba(OH)2+8H2O.    Mol.  Wt.  315.51 

White  crystals,  soluble  in  20  parts  of  cold,  and  in  3  parts  of 
boiling,  water,  a  trace  of  barium  carbonate  almost  invariably  remain- 
ing undissolved.  The  aqueous  solution  is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  barium  hydroxide  in  5  c.c.  of  nitric 
acid  and  25  c.c.  of  water  should  not  be  affected  by  silver  nitrate  solution.  (Indi- 
cating less  than  0.0005  per  cent  Cl.) 

Calcium  and  Alkalies.  —  Dissolve  3  gm.  of  barium  hydroxide  in  100  c.c.  of 
water,  add  5  c.c.  of  hydrochloric  acid,  and  heat  to  boiling.  Then  add  10  c.c. 
of  diluted  sulphuric  acid,  allow  to  stand  fifteen  hours,  and  filter.  On  evaporating 


BARIUM  HYDROXIDE  SOLUTION  53 


the  filtrate  in  a  platinum  dish  and  igniting,  a  residue  weighing  more  than  0.002 
gm.  should  not  remain.  (Indicating  not  more  than  0.0667  per  cent.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  barium  hydroxide  dissolved  in 
20  c.c.  of  water  should  not  acquire  a  dark  color,  or  yield  a  precipitate,  on  the 
addition  of  2  c.c.  hydrochloric  acid  followed  by  hydrogen  sulphide  water;  nor 
should  a  similar  solution  do  so  on  adding  ammonia  water  to  alkaline  reaction, 
followed  by  ammonium  sulphide  solution.  (Indicating  none  present.) 

Sulphides.  —  The  1  :  20  aqueous  solution  of  barium  hydroxide,  when  acid- 
ulated with  hydrochloric  acid,  should  not  have  an  odor  of  hydrogen  sulphide, 
nor  should  it  acquire  a  dark  color  on  adding  lead  acetate  solution.  (Indicating 
less  than  0.0027  per  cent  S.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  barium  hydroxide  in  100 
c.c.  of  water,  add  1  drop  of  methyl  orange  solution,  and  titrate  with  normal 
hydrochloric  acid.  Not  less  than  6.3  c.c.  of  the  normal  acid  should  be  necessary 
to  produce  the  red  end-point. 

1  c.c.  of  normal  HC1  =  0.157755  gm.  of  Ba(OH)2+8H20,  log.  19799. 

BARIUM  HYDROXIDE  SOLUTION 
(Baryta  Water) 

A  clear,  colorless  liquid,  of  strongly  alkaline  reaction.  Baryta 
water  contains  3.3  per  cent  of  crystallized  barium  hydroxide, 
Ba(OH)2+8H20. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Barium  Hydroxide.  But  for 
each  gram  of  crystallized  barium  hydroxide,  30  c.c.  of  baryta  water  are  to  be 
taken.  The  quantitative  determination  is  made  as  follows : 

Quantitative  Determination.  —  Titrate  50  c.c.  of  baryta  water  with  normal 
solution  of  hydrochloric  acid,  using  methyl  orange  as  the  indicator.  At  least 
10.5  c.c.  of  normal  solution  of  hydrochloric  acid  should  be  required  to  produce 
the  red  end-point. 

1  c.c.  of  normal  HC1  =  0.157755  gm.  of  Ba(OH)2+8H2O,  log.  19799. 

BARIUM   NITRATE 

Ba(NO3)2.    Mol.  Wt.  261.39 

Colorless  crystals,  soluble  in  20  parts  of  cold,  and  in  2.8  parts 
of  boiling,  water.  The  aqueous  solution  is  neutral  to  litmus  paper. 
Barium  nitrate  is  insoluble  in  absolute  alcohol. 

TESTS   OF  PURITY 

Chlorides.  —  The  1  :  20  aqueous  solution  acidulated  with  nitric  acid  should 
show  no  change  on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than 
0.0005  per  cent  Cl.) 

Alkalies  and  Heavy  Metals.  —  The  tests  are  to  be  carried  out  as  described 
under  Barium  Chloride.  In  the  test  for  alkalies  do  not  use  a  platinum  dish. 
0.002  gm.  residue  is  permissible.  (Indicating  not  more  than  0.0667  per  cent 
alkalies.) 


54  CHEMICAL  REAGENTS 


BARIUM  SULPHIDE 

Gray,  hard,  amorphous  pieces,  prepared  by  fusing  a  mixture  of 
heavy-spar,  powdered  coke,  and  sodium  chloride.  The  preparation 
contains  at  least  50  per  cent  of  barium  sulphide  (BaS),  and  is 
prepared  in  cube  form  for  generation  of  hydrogen  sulphide. 

On  allowing  hydrochloric  acid  to  flow  over  barium  sulphide, 
a  uniform  current  of  hydrogen  sulphide  should  be  generated. 

TESTS  OF  PURITY 

Arsenic.  —  Heat  100  c.c.  of  nitric  acid  (sp.gr.  1.3)  in  a  porcelain  dish  to  70° 
to  80°  C.,  and  add  10  gm.  of  finely  powdered  barium  sulphide,  gradually,  in 
quantities  of  0.2  to  0.3  gm.  at  a  time;  when  all  has  been  added,  heat  to  boiling. 
Then  add  to  the  mixture  100  c.c.  of  arsenic-free,  dilute  sulphuric  acid  (1  :  5), 
evaporate  on  the  water-bath  as  far  as  possible;  continue  to  heat  on  the  sand- 
bath  until  vapors  of  sulphuric  acid  begin  to  be  evolved;  cool,  and  finally  stir 
the  cooled  residue  with  100  c.c.  of  water. 

Set  a  Marsh  apparatus  in  operation,  using  20  gm.  of  arsenic-free,  granulated 
zinc  and  dilute  (1  :  5)  sulphuric  acid,  and  then  introduce  the  above  residue 
suspended  in  water,  in  small  quantities  at  a  time,  into  the  generating  flask  ot 
the  Marsh  apparatus.  No  deposit  of  arsenic  should  be  observable  in  the  reduction 
tube  after  the  apparatus  has  been  in  operation  one  hour.  (Indicating  less  than 
0.0001  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  0.73  gm.  of  copper  sulphate  (CuS04+ 
5H2O)  in  50  c.c.  of  water,  and  then  add  to  it  1  gm.  of  powdered  barium  sulphide, 
representing  the  average  quality  of  the  goods.  To  this  add,  while  stirring,  10 
c.c.  of  acetic  acid  (sp.gr.  1.040-1.042)  by  drops.  Filter,  expel  the  hydrogen 
sulphide  from  the  filtrate  by  boiling,  and  add  an  excess  of  ammonia  water. 
No  blue  color  should  appear.  (Indicating  at  least  50  per  cent  BaS.) 

NOTE.  —  This  chemical  serves  for  the  preparation  of  arsenic-free  hydrogen 
sulphide.  The  hydrochloric  acid  to  be  used  for  this  purpose  is  to  be  tested  for 
arsenic. 

BENZENE 

(Benzol) 

CeH6.    Mol.  Wt.  78.05 

A   clear,   colorless   liquid,   of   characteristic   odor,   insoluble   in 
water,  but  easily  soluble  in  alcohol  and  in  ether.     Benzene  upon 
cooling    forms  rhombic,  crystalline  scales,  which  melt  at  +4°  C. 
Its  specific  gravity  is  0.883,  and  it  boils  at  79-80°  C. 
TESTS   OF  PURITY 

Thiophene.*  —  On  shaking  50  c.c.  of  benzene  with  20  c.c.  of  concentrated 
sulphuric  acid,  the  sulphuric  acid  should  remain  colorless;  on  now  adding  a 

*See  C.  Schwalbe:  "The  Sulphur  Content  of  Pure  Benzenes";  Z.  Farb.- 
Textl.  Ind.,  3,  461  (1904);  abst.,  J.  Chem.  Soc.,  88,  1,  124  (1905).  Z.  Farb.- 
Textl.  Ind.,  4,  113  (1905);  abst.,  J.  Soc.  Chem.  Ind.,  24,  271  (1905). 


BENZIDINE  55 


crystal  of  isatin,  and  again  shaking  and  allowing  to  stand  one  hour,  the  sul- 
phuric acid  should  have  neither  a  green  nor  a  blue  color.  (Indicating  none 
present.) 

Carbon  Bisulphide.* — Thoroughly  mix  50  c.c.  of  benzene  with  50  c.c.  of 
alcoholic  potassium  hydroxide  solution  (11  gm.  of  potassium  hydroxide  in  90 
gm.  of  absolute  alcohol),  and  allow  the  mixture  to  stand  several  hours  at  a  tem- 
perature of  about  20°  C.  Shake  with  about  100  c.c.  of  water,  remove  the  aqueous 
solution  from  the  benzene,  neutralize  the  aqueous  portion  with  acetic  acid,  and 
add  copper  sulphate  solution.  No  precipitate  should  form.  (Indicating  less 
than  0.0072  per  cent  CS2.) 

BENZIDINE 

(Paradiaminodiphenyl) 

(C6H4)2(NH2)2.     Mol.  Wt.  184.12 

A  white  or  slightly  reddish  crystalline  powder,  melting  at  128° 
C.  Benzidine  is  very  difficultly  soluble  in  cold  water,  but  more 
readily  in  boiling  water,  in  alcohol,  and  in  ether. 

TEST  OF  PURITY 

Sulphates.  —  On  adding  barium  chloride  to  a  solution  of  1  gm.  of  benzidine 
in  50  c.c.  of  water  acidulated  with  5  c.c.  of  hydrochloric  acid,  no  precipitate  of 
barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating  less  than 
0.0125  per  cent  SO3.) 

Non-volatile  Matter.  —  1  gm.  of  benzidine  upon  ignition  should  leave  no 
weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

NOTE.  —  Regarding  the  use  of  benzidine  in  the  determination  of  sulphuric 
acid  see  Wolf  J.  Muller  and  K.  Durkes,  Z.  anal.  Chem.  42,  477  (1903);  abst., 
J.  Chem.  Soc.,  84,  II,  751  (1903).  W.  J.  Muller,  Z.  angew.  Chem.,  16,  653, 
1017  (1903);  abst.,  J.  Chem.  Soc.,  86,  II,  83  (1904).  Raschig,  Z.  angew.  Chem., 
16,  617  (1903);  abst.,  J.  Chem.  Soc.,  84,  II,  572  (1903).  Z.  angew.  Chem.,  16, 
818  (1903);  abst.,  J.  Chem.  Soc.,  84,  II,  691  (1903).  G.  Knorre,  J.  Soc.  Chem. 
Ind.,  28,  2  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  351  (1905).  Friedheim  and 
Nydegger,  Z.  angew.  Chem.,  20,  9  (1907);  abst.,  J.  Chem.  Soc.,  92,  II,  196  (1907). 
G.  Knorre,  Chem.  Ztg.,  34,  405  (1910);  abst.,  J.  Chem.  Soc.,  98,  II,  545  (1910). 

BENZIDINE  FOR  BLOOD  TEST 

(C6H4)2(NH2)2.    Mol.  Wt.  184.12 

A  light-brown,  crystalline  powder,  very  difficultly  soluble  in 
cold  water,  but  more  easily  soluble  in  boiling  water,  in  alcohol,  and 

in  ether. 

TEST  OF  PURITY 

Test  of  Suitability  for  Blood  Detection.  —  Dissolve  1  gm.  of  benzidine  in 
10  c.c.  of  concentrated  acetic  acid  (sp.gr.  1.064),  and  to  1  c.c.  of  this  solution 


*  F.  Frank:   Chem.  Ind.,  24,  237,  262  (1901)  [or  Chem.  Zentr.,  (5)  5,  1,  1251 
(1901)];  abst.,  J.  Soc.  Chem.    Ind.,  20,  563  (1901). 


56  CHEMICAL  REAGENTS 


add  10  c.c.  of  3  per  cent  solution  of  hydrogen  peroxide.*  No  color  at  all,  or  at 
most  a  very  faint  color  should  appear  within  a  few  minutes.  A  small  quantity 
of  blood  added  to  this  solution  produces  a  blue  color. 

NOTE.  —  Regarding  the  use  of  benzidine  for  detection  of  blood  see  O.  and 
R.  Adler,  Z.  physiol.  Chem.,  41,  59  (1904);  abst.,  J.  Chem.  Soc.,  86,  II,  459  (1904). 
O.  Schumm  and  C.  Westphal,  Z.  physiol.  Chem.,  46,  510  (1905);  abst.,  J.  Chem. 
Soc.,  90,  II,  207  (1906).  E.  Walter,  Deut.  med.  Wochenschr.,  35,  I,  130  (1909). 
Th.  Messerschmidt,  Munch,  med.  Wochenschr.,  56,  388  (1909);  abst.,  J.  Am. 
Med.  Assoc.,  52,  1150  (1909).  A.  Ascarelli,  Deut.  med.  Wochenschr.,  34,  II,  2307 
(1908);  abst.,  C.  A.,  3,  I,  764  (1909).  F.  W.  White,  Boston  Med.  and  Surg. 
Jour.,  160,  733  (1909).  H.  Merkel,  Munch,  med.  Wochenschr.,  56,  II,  2358  (1909), 
abst.,  C.  A.,  4,  I,  334  (1910).  O.  Schumm,  Arch.  d.  Pharm.,  247,  16  (1909);  abst., 
J.  Chem.  Soc.,  96,  II,  195  (1909).  E.  Schlesinger  and  F.  Hoist,  Deut.  med. 
Wochenschr.,  32,  II,  1444  (1906);  abst.,  J.  Am.  Med.  Assoc.,  47,  1335  (1906).  O. 
Schumm,  Deut.  med.  Wochenschr.,  33,  II,  1471  (1907);  abst.,  J.  Chem.  Soc.,  92, 
II,  827  (1907).  E.  Walter,  Deut.  med.  Wochenschr.,  36,  I,  309  (1910);  abst.,  C. 
A.,  4,  1184  (1910).  M.  Einhorn,  Deut.  med.  Wochenschr.,  33,  II,  1089  (1907); 
abst.,  J.  Am.  Med.  Assoc.,  48,  2161  (1907),  and  Med.  Record,  June  8  (1907). 
Utz,  Chem.  Ztg.,  31,  737  (1907);  abst.,  J.  Chem.  Soc.,  92,  II,  916  (1907). 


BENZIN 
(Petroleum  Ether;  Petroleum  Benzin) 

A  colorless,  non-fluorescent,  very  inflammable  liquid  consisting 
of  the  low-boiling  portions  of  petroleum,  and  having  a  characteristic 
but  not  unpleasant  odor.  Specific  gravity  0.666  to  0.686.  Benzin 
does  not  solidify  at  0°  C.  If  100  c.c.  are  heated  on  the  water-bath 
at  least  80  c.c.  will  distill  between  40°  and  70°  C. 

TESTS   OF  PURITYf 

Non-volatile  Matter  and  Heavy  Oils.  —  20  c.c.  of  benzin  warmed  on  the 
water-bath  should  volatilize  and  leave  no  residue.  When  dropped  upon  paper, 
and  allowed  to  evaporate,  it  should  leave  no  greasy  spot.  (Indicating  none 
present.) 

Acids.  —  10  c.c.  of  benzin  shaken  with  10  c.c.  of  water  should  not  impart  to 
the  water  an  acid  reaction.  (Indicating  none  present.) 

Sulphur  Compounds  and  Reducing  Substances.  —  A  mixture  of  5  c.c.  of 
benzin  and  10  c.c.  of  alcoholic  ammoniacal  silver  nitrate  solution J  is  heated 
on  a  water-bath  protected  from  the  light.  No  brown  color  should  appear  within 
five  minutes.  (Indicating  none  present.) 


*1  c.c.  perhydrol+9  c.c.  water. 

f  The  testing  of  benzin  for  benzene  by  nitrating  the  latter  with  nitro-sulphuric 
acid  was  not  adopted  here,  because  it  is  impossible  to  obtain  a  benzin  that  will 
stand  this  test. 

J  10  c.c.  of  a  solution  of  1  gm.  of  silver  nitrate  in  100  c.c.  of  alcohol  (about 
85  per  cent  by  weight)  are  mixed  with  5  c.c.  of  an  alcoholic  solution  of  ammonia 
(9-10  per  cent  NH8.). 


BISMUTH  SUBNITRATE  57 

BISMUTH  SUBNITRATE 
(Bismuth  Basic  Nitrate) 

A  white,  microcrystalline  powder,  insoluble  in  water  and  in 
alcohol,  but  soluble  in  diluted  hydrochloric,  nitric,  or  sulphuric 
acid.  It  contains  70.8-73.5  per  cent  bismuth,  Bi.  On  shaking 
bismuth  subnitrate  with  water,  it  imparts  an  acid  reaction  to  the 

latter. 

TESTS  OF  PURITY 

Carbonates,  Lead,  Copper,  Salts  of  the  Alkalies,  etc.  —  0.5  gm.  of  bismuth 
subnitrate  should  completely  dissolve  in  25  c.c.  of  cold  16  per  cent  sulphuric 
acid  without  the  evolution  of  carbon  dioxide  (indicating  no  carbonate  present), 
and  should  yield  a  clear  solution  (indicating  less  than  0.165  per  cent  Pb).  10  c.c. 
of  this  solution,  with  an  excess  of  ammonia  water,  should  yield  a  colorless  filtrate. 
(Indicating  less  than  0.01  per  cent  Cu.)  Another  10  c.c.  of  this  solution, 
diluted  with  100  c.c.  of  water  and  treated  with  hydrogen  sulphide  to  precipitate 
completely  the  bismuth,  should  yield  a. filtrate  leaving  no  weighable  residue  on 
evaporation  and  ignition.  (Indicating  less  than  0.25  per  cent  alkali  salts.) 

Chlorides.  —  On  adding  silver  nitrate  solution  to  a  solution  of  0.5  gm.  of 
bismuth  subnitrate  in  5  c.c.  of  nitric  acid,  not  more  than  a  slight  opalescent 
turbidity  should  develop.  (Indicating  less  than  0.01  per  cent  Cl.) 

Sulphates.  —  The  solution  of  0.5  gm.  of  bismuth  subnitrate  in  5  c.c.  of 
nitric  acid  should  show  no  change  on  the  addition  of  5  c.c.  of  water  followed  by 
5  to  10  drops  of  barium  nitrate  solution.  (Indicating  less  than  1.5  per  cent  SO3.) 

Ammonia.  —  On  warming  1  gm.  of  bismuth  subnitrate  with  10  c.c.  of  sodium 
hydroxide  solution  (sp.gr.  1.3),  no  ammonia  should  be  evolved  (to  be  ascertained 
by  moistened  litmus  paper).  (Indicating  less  than  0.0035  per  cent  NH3.) 

Residue  on  Ignition.  —  On  igniting  1  gm.  of  bismuth  subnitrate,  there  should 
remain  a  residue  of  bismuth  oxide  weighing  0.79  to  0.82  gm.  (Indicating  79  to  82 
per  cent.) 

Arsenic.  —  The  residue  of  bismuth  oxide  obtained  above  is  triturated  to  a 
fine  powder,  and  dissolved  in  sulphuric  acid  with  heat.  Set  a  Marsh  apparatus 
in  operation,  using  20  gm.  of  arsenic-free,  granulated  zinc,  and  dilute  (1  :  5) 
sulphuric  acid,  then  introduce  the  bismuth  solution  into  the  evolution  flask. 
No  deposit  of  arsenic  should  be  visible  in  the  reduction  tube  within  half  an  hour. 
(Indicating  less  than  0.001  per  cent  As.) 

BISMUTH  AND   POTASSIUM  IODIDE  SOLUTION 

An  aqueous  solution  containing  in  each  kilo  25  gm.  of  bismuth 
iodide  and  100  gm.  of  potassium  iodide. 

BROMINE 
Br.    Atomic  Wt.  79.92 

A  dark-red  to  brown,  almost  black,  liquid,  of  specific  gravity 
3.14,  and  boiling  at  about  63°  C.  Bromine  dissolves  in  about  30 


58  CHEMICAL  REAGENTS 

parts  of  water.     It  is  easily  soluble  in  alcohol,  ether,  chloroform, 
and  carbon  disulphide. 

TESTS   OF  PURITY 

Non- volatile  Matter.  —  5  gm.  of  bromine  warmed  in  a  porcelain  dish  on  the 
water-bath  should  volatilize  and  leave  no  weighable  residue.  (Indicating  less 
than  0.01  per  cent.) 

Sulphuric  Acid  and  Organic  Bromine  Compounds  (Bromoform;  Carbon 
Tetrabrpmide) .  —  2  gm.  of  bromine  should  dissolve  clear  in  a  mixture  of  10  c.c. 
of  solution  of  sodium  hydroxide  (sp.gr.  1.168-1.172),  and  10  c.c.  of  water.  After 
standing  six  hours  no  oily  drops  should  be  visible  in  this  solution.  (Indicating 
no  organic  bromine  compounds  present.)  If  the  solution  is  then  acidulated  with 
hydrochloric  acid  and  boiled  until  the  bromine  has  volatilized,  the  addition  of 
barium  chloride  solution  should  cause  no  apparent  change.  (Indicating  less 
than  0.005  per  cent  SO3.) 

Iodine.  —  Dissolve  1  gm.  of  bromine  in  40  c.c.  of  water,  add  4  gm.  of  powdered 
iron,  and  shake  two  to  three  minutes.  Filter,  add  starch  solution  and  ferric 
chloride  solution  to  the  filtrate.  No  blue  color  should  appear.  (Indicating 
less  than  0.75  per  cent  I.) 

Determination  of  Chlorine  Content.  —  Tare  a  graduated  250  c.c.  flask  con- 
taining 15  gm.  of  potassium  iodide  and  30  c.c.  of  water.  Add  about  1  c.c.  of 
water-free  bromine  and  weigh.  After  complete  solution  of  the  iodine,  dilute 
to  the  mark,  mix,  and  titrate  25  c.c.  of  the  liquid  with  decinormal  solution  of 
sodium  thiosulphate.  If  A  is  the  amount  of  bromine  weighed  off,  and  /  the 

j i  sggA 

amount  of  iodine  liberated,  and  X  the  amount  of  chlorine  in  A,  then  X  =  —  '  . 

J-  .  Jt-7  1  *j 

The  bromine  is  A  —X. 

1  c.c.  of  decinormal  Na2S203  =  0.012692  gm.  of  I,  log.  10352. 

BROMINE  WATER 

A  saturated,  aqueous  solution,  containing  about  3  per  cent  of 

bromine,  Br. 

TESTS   OF  PURITY 

Sulphuric  Acid.  —  Add  1  c.c.  of  hydrochloric  acid  and  some  barium  chloride 
solution  to  50  c.c.  of  bromine  water,  and  boil  the  liquid  until  the  bromine  has 
been  completely  expelled  from  it.  No  precipitate  of  barium  sulphate  should 
separate  on  standing.  t  (Indicating  less  than  0.00002  per  cent  SO3.) 

Bromine  Content.' — Let  10  c.c.  of  bromine  water  run  into  a  solution  of  5 
gm.  of  potassium  iodide  in  100  c.c.  of  water,  allow  to  stand  half  an  hour  in  a 
stoppered  flask,  and  then  titrate  with  decinormal  sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3  =  0.007992  gm.  of  Br.,  log.  90266. 

BRUCINE 
C23H26N2O4+2H2O.*    Mol.  Wt.  430.36 

Small,  white  crystals,  difficultly  soluble  in  cold,  but  more  readily 
soluble  in  boiling,  water.  Brucine  is  easily  soluble  in  alcohol  (85 


*  Brucine  also  crystallizes  with  4  molecules  of  water;    then  it  dissolves  in 
320  parts  of  cold,  and  in  150  parts  of  boiling,  water. 


CADMIUM  BOROTUNGSTATE  SOLUTION  59 

per  cent  by  weight),  and  in  chloroform.  The  aqueous  solution  of 
brucine  is  alkaline  to  litmus  paper,  and  is  levogyrate.  When  dried 
at  100°  C.,  brucine  melts  at  178°  C. 

TESTS   OF  PURITY 

Water  of  Crystallization.  —  1  gm.  of  brucine  dried  at  JOO0  C.  to  constant 
weight  should  lose  not  more  than  0.084  gm.  (Indicating  not  more  than  8.4  per 
cent.) 

Nitric  Acid.  —  0.01  gm.  of  brucine  should  dissolve  in  5  c.c.  of  pure  concentrated 
sulphuric  acid,  and  the  solution  should  be  colorless  or,  at  most,  of  a  scarcely 
perceptible  faint  pink  color.*  (Indicating  less  than  0.05  per  cent  N^Os.) 

Quantitative  Determination.  —  Dissolve  0.25  gm.  of  brucine  in  50  c.c.  of 
alcohol  (85  per  cent  by  weight),  and  titrate  with  decinormal  hydrochloric  acid, 
using  lacmoid  as  the  indicator.  At  least  5.8  c.c.  of  decinormal  acid  should  be 
required  to  produce  the  red  end-point. 

1  c.c.  of  decinormal  HC1  =  0.043026  gm.  of  C23H26N2O4+2H2O,  log.  63373. 


CADMIUM   BOROTUNGSTATE   SOLUTION 

A  perfectly  clear,  yellowish,  or  light  brown,  liquid,  having  a 
specific  gravity  of  3.28. 


CADMIUM   AND   POTASSIUM  IODIDE 
(Potassium-Cadmium  Iodide) 

A  white  powder,  easily  soluble  in  water,  and  in  alcohol.  Cadmium 
and  potassium  iodide  readily  acquires  a  slight  yellowish  color  on 
keeping. 

TESTS   OF  PURITY 

Foreign  Metals.  —  (a)  Dissolve  1  gm.  of  cadmium  and  potassium  iodide  in 
20  c.c.  of  water,  add  to  the  solution  2  c.c.  of  potassium  hydroxide  solution  (sp.gr. 
1.138-1.140),  and  filter.  Neither  before  nor  after  acidulating  with  hydrochloric 
acid  should  the  filtrate  yield  a  precipitate  with  hydrogen  sulphide  water.  (Indi- 
cating none  present.) 

(6)  Dissolve  1  gm.  of  cadmium  and  potassium  iodide  in  30  c.c.  of  water, 
and  add  to  the  solution  5  c.c.  of  ammonia  water.  The  liquid  should  remain 
clear  and  colorless  on  shaking.  (Indicating  none  present.) 

Sulphates.  —  The  1  :  20  aqueous  solution  acidulated  with  hydrochloric  acid 
should  not  be  affected  by  barium  chloride  solution.  (Indicating  less  than 
0.01  per  cent  SO3.) 

Ipdic  Acid.  —  The  1  :  20  solution  freshly  prepared  with  boiled  water  should 
not  immediately  give  a  blue  color  on  adding  starch  solution  followed  by  2  or  3 
drops  of  dilute  sulphuric  acid.  (Indicating  less  than  0.00125  per  cent  HIO3.) 


*  The  sulphuric  acid  should  be  tested  with  diphenylamine  to  insure  the 
absence  of  nitric  acid. 


60  CHEMICAL  REAGENTS 

CALCIUM  CARBONATE  PRECIPITATED 
CaCO3.    Mol.  Wt.  100.07 

A  white,  crystalline  powder,  insoluble  in  boiled  water,  but 
somewhat  soluble  in  carbonated  water. 

TESTS  OF  PURITY 

Solubility  in  Hydrochloric,  Nitric,  and  Acetic  Acids.  —  5  gm.  of  calcium  car- 
bonate should  be  completely  dissolved  by  25  c.c.  of  hydrochloric  acid,  by 
25  c.c.  of  nitric  acid,  and  by  60  c.c.  of  30  per  cent  acetic  acid.  The  solutions 
must  be  clear  and  colorless. 

Heavy  Metals.  —  Dissolve  1  gm.  of  calcium  carbonate  in  5  c.c.  of  hydrochloric 
acid  and  25  c.c.  of  water.  This  solution  should  not  appear  changed  upon  adding 
hydrogen  sulphide  water;  then  upon  adding  ammonia  water  in  excess  accom- 
panied by  2  or  3  drops  of  ammonium  sulphide  solution  neither  a  green  color 
nor  a  precipitate  should  appear.  (Indicating  none  present.) 

Magnesium.  —  Dissolve  1  gm.  of  calcium  carbonate  in  5  c.c.  of  hydrochloric 
acid  and  5  c.c.  of  water.  To  this  solution  add  10  c.c.  of  ammonia  water  and  an 
excess  of  ammonium  oxalate  solution,  allow  to  stand  five  hours,  filter,  and  add 
to  the  filtrate  sodium  phosphate  solution.  No  precipitate  should  form  on  stand- 
ing fifteen  hours.  (Indicating  less  than  0.002  per  cent  Mg.) 

Sulphates.  —  Dissolve  1  gm.  of  calcium  carbonate  in  5  c.c.  of  hydrochloric 
acid  and  25  c.c.  of  water,  boil  the  solution  five  minutes,  and  add  barium  chloride 
solution.  No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen 
hours.  (Indicating  less  than  0.0125  per  cent  SO3.) 

Chlorides.  —  1  gm.  of  calcium  carbonate  dissolved  in  5  c.c.  of  nitric  acid 
and  25  c.c.  of  water,  must  show  no  change  on  the  addition  of  silver  nitrate  solu- 
tion. (Indicating  less  than  0.0005  per  cent  Cl.) 

Phosphates.  —  Dissolve  10  gm.  of  calcium  carbonate  in  50  c.c.  of  nitric  acid, 
add  25  c.c.  of  ammonium  molybdate  solution,  and  allow  to  stand  fifteen  hours 
at  a  temperature  of  30°  to  40°  C.  No  yellow  precipitate  should  form.  (Indi- 
cating less  than  0.001  per  cent  P2O5.) 

Alkalies  and  Calcium  Oxide.  —  Boil  5  gm.  of  calcium  carbonate  with  50 
c.c.  of  water  and  then  filter.  The  filtrate  should  not  be  alkaline  to  litmus,  and 
upon  evaporation  followed  by  ignition  should  leave  a  residue  weighing  at  most 
0.001  gm.  (Indicating  not  more  than  0.02  per  cent.) 

CALCIUM  CHLORIDE  CRYSTALS 
CaCl2+6H2O.    Mol.  Wt.  219.09 

Colorless  crystals,  deliquescent  in  the  air,  and  easily  soluble  in 
water  and  in  alcohol.  The  1  :  10  solution  should  be  neutral  to  litmus 

paper. 

TESTS   OF  PURITY 

Substances  Insoluble  in  Absolute  Alcohol.  —  2  gm.  of  calcium  chloride 
should  completely  dissolve  in  20  c.c.  of  absolute  alcohol.  (Indicating  none 
present.) 


CALCIUM  CHLORIDE  61 


Heavy  Metals.  —  20  c.e.  of  the  1  :  10  aqueous  solution  should  show  no  change 
on  adding  1  c.c.  of  hydrochloric  acid  and  hydrogen  sulphide  water.  On  further 
adding  5  c.c.  of  ammonia  water  and  2  to  3  drops  of  ammonium  sulphide  solution, 
no  green  color  should  develop,  nor  should  a  precipitate  form.  (Indicating  none 
present.) 

Sulphates.  —  On  adding  barium  chloride  solution  to  the  solution  of  2  gm. 
of  calcium  chloride  in  20  c.c.  of  water  acidulated  with  1  c.c.  of  hydrochloric  acid, 
no  precipitate  should  form  on  standing  fifteen  hours.  (Indicating  less  than 
0.0038  per  cent  SO3.) 

Ammonium  Salts.  —  On  boiling  2  gm.  of  calcium  chloride  with  10  c.c.  of 
sodium  hydroxide  solution,  no  ammonia  should  be  evolved  (to  be  ascertained 
by  moistened  litmus  paper).  (Indicating  less  than  0.00175  per  cent  NH3.) 

Barium.  —  On  adding  20  c.c.  of  calcium  sulphate  solution  to  the  solution 
of  2  gm.  of  calcium  chloride  in  20  c.c.  of  water,  no  change  should  appear  within 
three  hours.  (Indicating  less  than  0.002  per  cent  Ba.) 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  granulated  metallic  zinc  into  the 
generating  flask  of  a  Marsh  apparatus,  and  start  the  hydrogen  with  dilute  (1:5) 
sulphuric  acid.  Dissolve  5  gm.  of  calcium  chloride  in  20  c.c.  of  water,  introduce 
the  solution  into  the  Marsh  apparatus,  and  maintain  the  stream  of  gas  for  one 
hour.  No  deposit  of  arsenic  should  be  visible  in  the  reduction  tube  within 
this  time.  (Indicating  less  than  0.0002  per  cent  As.) 

Nitrates.  —  A  solution  of  1  gm.  of  calcium  chloride  in  10  c.c.  of  water  is 
mixed  with  one  drop  of  indigo  solution  (1  :  1000)  and  10  c.c.  of  concentrated 
sulphuric  acid.  (Caution!  Hydrochloric  acid  is  freely  evolved!)  The  blue 
color  of  the  solution  should  not  disappear  upon  shaking.  (Indicating  less  than 
0.0032  per  cent  N205.) 


CALCIUM   CHLORIDE,  DRY,   GRANULATED 
CaCl2+2H2O.     Mol.  Wt.  147.02 

White,  granular,  porous  masses  in  pieces  the  size  of  peas.  It  may 
be  used  for  drying  gases. 

TESTS   OF  PURITY 

Neutrality.  —  The  solution  of  10  gm.  of  calcium  chloride  in  100  c.c.  of  water 
must  not  turn  phenolphthalein  red.  At  most  a  very  slight  red  may  occur. 
Any  red  color  must  be  discharged  by  the  addition  of  0.1  c.c.  of  decinormal 
hydrochloric  acid.  (Indicating  not  more  than  0.0028  per  cent  CaO.) 

Arsenic.  —  The  test  to  be  carried  out  and  conditions  to  be  observed  are 
those  given  under  Calcium  Chloride  Crystals.  (Indicating  less  than  0.0002 
per  cent  As.) 

CALCIUM   CHLORIDE,  FUSED 

White  crystalline  masses,  the  formula  of  which  is  practically 
CaCl2.  Fused  calcium  chloride  is  chiefly  used  for  drying  liquids, 
e.g.,  ethers,  esters,  ethereal  oils,  hydrocarbons,  etc. 


62  CHEMICAL  REAGENTS 

CALCIUM  HYDROXIDE 

(Slaked  Lime) 
Ca(OH)2.    Mol.  Wt.  71.09 

A  white,  dry  powder. 

The  article  is  tested  as  to  purity  by  the  methods  detailed  under 
Calcium  Oxide,  from  Marble. 

CALCIUM   OXIDE,  FROM  ICELAND   SPAR 

CaO.    Mol.  Wt.  56.07 

White  pieces  in  the  form  of  Iceland  spar  crystals. 
TESTS   OF  PURITY 

Carbonates,  Silicates,  and  Sulphates.  —  3  gm.  of  calcium  oxide  slaked  with 
10  c.c.  of  water  should  completely  dissolve  in  15  c.c.  of  hydrochloric  acid  without 
effervescence.  (Indicating  less  than  0.7  per  cent  CO2,  and  no  silicates  present.) 
Dilute  the  solution  with  50  c.c.  of  water,  heat  to  boiling,  and  add  barium  chloride 
solution.  On  standing  fifteen  hours,  not  more  than  a  scarcely  perceptible, 
unweighable  trace  of  barium  sulphate  should  be  present.  (Indicating  less  than 
0.017  per  cent  SO3.) 

Phosphates.  —  Dissolve  3  gm.  of  calcium  oxide  in  10  c.c.  of  water,  mixed  with 
25  c.c.  of  nitric  acid,  and  add  25  c.c.  of  ammonium  molybdate  solution.  No 
yellow  precipitate  should  form  on  standing  fifteen  hours  at  about  40°  C.  (Indi- 
cating less  than  0.0033  per  cent  P2O6.) 

Chlorides.  —  Dissolve  3  gm.  of  calcium  oxide  in  10  c.c.  of  water  mixed  with 
25  c.c.  of  nitric  acid,  ^he  solution  should  show  no  change  on  the  addition  of 
silver  nitrate  solution.  (Indicating  less  than  0.00015  per  cent  Cl.) 

Iron.  —  Dissolve  1  gm.  of  calcium  oxide  in  10  c.c.  of  water  mixed  with  10 
c.c.  of  hydrochloric  acid.  The  solution  should  not  immediately  afford  a  blue 
color  on  adding  0.5  c.c.  of  potassium  ferrocyanide  solution.  (Indicating  less 
than  0.01  per  cent  Fe.) 

CALCIUM   OXIDE,  FROM   MARBLE 

(Lime) 
CaO.    Mol.  Wt.  56.07 

White  pieces  of  granular  structure  which  develop  much  heat  on 
being  sprinkled  with  half  their  weight  of  water,  and  become  con- 
verted into  a  fine,  dust-like  powder  of  slaked  lime.  With  three  or 
four  parts  of  water  the  slaked  lime  yields  a  thick  paste.  Calcium 
oxide  is  soluble  in  about  800  parts  of  cold,  and  in  1300  parts  of 
boiling,  water. 


CALCIUM  PHOSPHATE  68 


TESTS   OF  PURITY 

Carbonates,  Silica,  Alumina,  and  Sulphates.  —  Slake  5  gm.  of  calcium  oxide 
with  10  c.c.  of  water.  The  magma  so  obtained  should  almost  completely  dis- 
solve in  30  c.c.  of  hydrochloric  acid  without  strong  effervescence.  (Indicating 
less  than  5  per  cent  CO2.)  Dilute  the  solution  with  20  c.c.  of  water,  and  filter. 
The  insoluble  residue,  after  washing  and  ignition,  should  weigh  at  most  0.005 
gm.  (Indicating  not  more  than  0.1  per  cent  SiO2.)  To  25  c.c.  of  the  filtrate, 
add  barium  chloride  solution;  the  liquid  should  show  no  change  within  ten 
minutes.  (Indicating  less  than  0.03  per  cent  SOs.)  Supersaturate  25  c.c.  of 
the  filtrate  with  ammonia  water;  the  liquid  should  not  contain  more  than  a 
slight  flocculent  precipitate.  (Indicating  less  than  0.25  per  cent  Al.) 

Chlorides.  —  Dissolve  1  gm.  of  calcium  oxide  in  10  c.c.  of  water,  mixed  with 
10  c.c.  of  nitric  acid,  and  add  silver  nitrate  solution.  The  liquid  should  not  be 
rendered  more  than  slightly  opalescent.  (Indicating  less  than  0.002  per  cent  Cl.) 

CALCIUM  PHOSPHATE,  DIBASIC 

(Secondary  Calcium  Phosphate;  Dicalcium  Phosphate) 
CaHPO4+2H2O.     Mol.  Wt.  172.15 

A  white,  crystalline  powder,  easily  soluble  in  hydrochloric, 
nitric,  or  phosphoric  acid,  without  effervescence;  it  is  difficultly 
soluble  in  water. 

Dicalcium  phosphate  does  not  dissolve  in  boiling  water  without 
decomposition;  it  produces  a  liquid  of  acid  reaction,  and  an  amor- 
phous residue  the  composition  of  which  approximates  that  of  the 
neutral  salt. 

TESTS   OF  PURITY 

Arsenic.  —  The  test  is  carried  out  as  described  under  Calcium  Phosphate, 
Monobasic,  on  page  64,  using  a  solution  of  2  gm.  of  dicalcium  phosphate  in  5 
c.c.  of  hydrochloric  acid  and  15  c.c.  of  water.  (Indicating  less  than  0.0005 
per  cent  As.) 

Chlorides.  —  Dissolve  1  gm.  of  dicalcium  phosphate  in  5  c.c.  of  nitric  acid 
and  15  c.c.  of  water;  on  adding  silver  nitrate  solution,  not  more  than  a  slight 
opalescent  turbidity  should  be  visible.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  dicalcium  phosphate  in  5  c.c.  of 
hydrochloric  acid  and  15  c.c.  of  water  should  afford  a  pure  white  precipitate  on 
the  addition  of  hydrogen  sulphide  water  and  10  c.c.  of  ammonia  water.  (Indi- 
cating none  present.) 

Sulphates.  —  On  shaking  1  gm.  of  dicalcium  phosphate  with  20  c.c.  of  water 
and  filtering,  the  filtrate,  on  adding  1  c.c.  of  hydrochloric  acid  and  barium 
chloride  solution,  should  develop  no  precipitate  within  fifteen  hours.  (Indicating 
less  than  0.0075  per  cent  SOS.) 

Residue  on  Ignition.  —  On  ignition,  dicalcium  phosphate  should  yield  74 
to  75  per  cent  of  its  weight  of  residue.* 


*  On  ignition,  dicalcium  phosphate  is  converted  into  calcium  pyrophosphate, 
whereby  it  theoretically  loses  26.12  per  cent  of  water. 


64  CHEMICAL  REAGENTS 


CALCIUM  PHOSPHATE,  MONOBASIC 

(Calcium  Biphosphate;    Calcium  Acid   [or  Super]  Phosphate; 
Primary  Calcium  Phosphate;  Monocalcium  Phosphate) 

Ca(H2P04)2+H20.    Mol.  Wt.  252.2 

Colorless,  pearly  scales,  which  readily  deliquesce  in  the  air. 

Calcium  biphosphate  dissolves  in  much  water,  apparently  without 
decomposition;  with  a  small  quantity  of  water,  an  amorphous 
salt  separates,  richer  in  calcium,  while  the  solution  exhibits  a 
strongly  acid  reaction. 

On  heating  a  1  :  50  aqueous  solution  of  calcium  biphosphate 
to  boiling,  a  precipitate  forms. 

TESTS  OF  PURITY 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  granulated  zinc  into  the  gen- 
erating flask  of  a  Marsh  apparatus,  and  start  the  stream  of  hydrogen  by  adding 
dilute  (1  :  5)  sulphuric  acid.  After  the  apparatus  and  reagents  have  been  tested 
in  the  usual  manner,  dissolve  2  gm.  of  calcium  biphosphate  in  5  c.c.  of  hydrochloric 
acid  and  15  c.c.  of  water.  Introduce  this  solution  into  the  Marsh  apparatus, 
and  maintain  the  flow  of  gas  for  one  hour.  No  deposit  of  arsenic  should  be 
visible  in  the  reduction  tube  within  this  time.  (Indicating  less  than  0.0005 
per  cent  As.) 

Chlorides.  —  A  solution  of  1  gm.  of  calcium  biphosphate  in  5  c.c.  of  nitric 
acid  and  15  c.c.  of  water  should  not  be  rendered  more  than  slightly  opalescent 
on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  On  adding  hydrogen  sulphide  water  and  10  c.c.  of  ammonia 
water  to  a  solution  of  1  gm.  of  calcium  biphosphate  in  5  c.c.  of  hydrochloric 
acid  and  15  c.c.  of  water,  a  pure  white  precipitate  should  form.  (Indicating 
none  present.) 

Sulphates.  —  1  gm.  of  calcium  biphosphate  dissolved  in  5  c.c.  of  hydrochloric 
acid  and  20  c.c.  of  water  should  not  be  changed  by  the  addition  of  barium 
chloride  solution.  (Indicating  less  than  0.0875  per  cent  SO3.) 

CALCIUM  PHOSPHATE,  TRIBASIC 
(Tertiary  Calcium  Phosphate;  Tricalcium  Phosphate) 

Ca3(PO4)2.    Mol.  Wt.  310.29 

A  white,  amorphous  powder,  insoluble  in  cold  water.  Tri- 
calcium phosphate  is  gradually  decomposed  by  boiling  water  into 
an  insoluble  basic  salt  and  an  easily  soluble  acid  salt.  It  is  easily 
soluble  in  hydrochloric  or  nitric  acid,  and  without  effervescence. 

TESTS   OF  PURITY 

Arsenic.  —  The  test  is  carried  out  as  detailed  under  Calcium  Phosphate, 
Monobasic,  see  above,  using  a  solution  of  2  gm.  of  tricalcium  phosphate  in 


CALCIUM  SULPHATE  65 


5  c.c.  of  hydrochloric  acid  and  15  c.c.  of  water.  (Indicating  less  than  0.0005 
per  cent  As.) 

Sulphates.  —  Shake  1  gm.  of  tricalcium  phosphate  with  20  c.c.  of  water, 
filter,  and  add  to  the  filtrate  1  c.c.  of  hydrochloric  acid  and  barium  chloride 
solution.  No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen 
hours.  (Indicating  less  than  0.0075  per  cent  SO3.) 

Chlorides.  —  The  solution  of  1  gm.  of  tricalcium  phosphate  in  5  c.c.  of  nitric 
acid  and  15  c.c.  of  water  should  not  show  more  than  a  slight  opalescent  turbidity 
on  adding  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  tricalcium  phosphate  in  5  c.c.  of 
hydrochloric  acid  and  15  c.c.  of  water  should  yield  a  pure  white  precipitate  on 
adding  hydrogen  sulphide  water  and  10  c.c.  of  ammonia  water.  (Indicating 
none  present.) 

CALCIUM   SULPHATE 

(Gypsum) 

CaSO4+2H2O.     Mol.  Wt.  172.17 
A  fine  white  powder,  difficultly  soluble  in  water  (about  1  '  500) . 

TESTS   OF  PURITY 

Iron,  Magnesium,  and  Alkalies.  —  On  warming  2  gm.  of  calcium  sulphate  with 
10  c.c.  of  hydrochloric  acid  and  100  c.c.  of  water,  a  clear  solution  should  result, 
which,  on  the  addition  of  15  c.c.  of  ammonia  water  and  a  few  drops  of  ammonium 
sulphide  solution,  should  not  acquire  a  greenish  or  dark  color.  (Indicating  less 
than  0.00375  per  cent  Fe.)  To  the  solution,  no  matter  whether  a  precipitate  of 
calcium  sulphate  has  formed  or  not,  add  ammonium  oxalate  solution  in  slight 
excess,  filter,  evaporate  the  filtrate,  and  ignite  in  a  platinum  dish.  There  should 
not  remain  a  residue  weighing  more  than  0.002  gm.  (Indicating  not  more 
than  0.1  per  cent  magnesium  and  alkalies.) 

CALCIUM   SULPHIDE 

(Sulphurated  Lime) 

Bulky,  light-gray  cubes,   from  which  dilute  hydrochloric  acid 
sets  free  copious  quantities  of  hydrogen  sulphide  gas.     The  prepa- 
ration contains  at  least  60  per  cent  calcium  sulphide  (CaS). 
TESTS   OF  PURITY 

Arsenic.  —  This  is  carried  out  as  detailed  under  Barium  Sulphide  on  page 
54.  (Indicating  less  than  0.0001  per  cent  As.) 

Quantitative  Determination.  —  Into  a  solution  of  2.08  gm.  of  copper  sulphate 
(CuSO4+5H2Q)  in  50  c.c.  of  water  introduce  1  gm.  of  powdered  calcium  sulphide, 
and  while  stirring  add  by  drops  10  c.c.  of  hydrochloric  acid.  Warm  the  mixture 
about  fifteen  minutes  on  the  water-bath  and  then  filter.  The  filtrate  upon  the 
addition  of  ammonia  water  in  excess  must  show  no  blue  color.  (Indicating  at  least 
60  per  cent  of  CaS.) 

NOTE.  —  This  preparation  serves  for  the  generation  of  arsenic-free  hydrogen 
sulphide.  The  hydrochloric  acid  used  for  this  purpose  should  also  be  tested 
or  arsenic. 


66  CHEMICAL  REAGENTS 

CARBON  BISULPHIDE 
CS2.    Mol.  Wt.  76.14 

A  clear,  colorless,  neutral  liquid  of  specific  gravity  1.270  to 
1.272,  and  boiling  at  46°  to  47°  C.  Carbon  disulphide  is  insoluble  in 
water,  but  is  miscible  in  all  proportions  with  alcohol  and  ether. 

TESTS   OF  IURITY 

Non-volatile  Matter.*  —  On  evaporating  50  c.c.  of  carbon  disulphide  on  the 
water-bath,  no  weighable  residue  should  remain.  (Indicating  less  than  0.0008 
per  cent.) 

Hydrogen  Sulphide  and  Foreign  Organic  Sulphur  Compounds.  —  (a)  On 
shaking  10  c.c.  of  carbon  disulphide  with  lead  carbonate,  the  latter  should  not 
acquire  a  brown  color.  (Indicating  none  present.) 

(6)  On  shaking  2  c.c.  of  carbon  disulphide  in  a  dry  vessel  with  a  globule  of 
bright  metallic  mercury,  the  bright  surface  of  the  latter  should  not  become 
covered  with  a  dark,  pulverulent  coating.  (Indicating  none  present.) 

Sulphuric  and  Sulphurous  Acids.  —  On  shaking  10  c.c.  of  carbon  disulphide 
with  5  c.c.  of  water,  the  latter  should  neither  redden  nor  decolorize  blue  litmus 
paper.  (Indicating  none  present.) 

CARBON  TETRACHLORIDE 

CC14.     Mol.  Wt.  153.84. 

A  clear,  colorless  liquid  only  slightly  soluble  in  water  (about 
0.08  parts  to  100).  Carbon  tetrachloride  is  miscible  in  all  propor- 
tions with  absolute  alcohol,  ether,  and  with  ethereal  and  fatty  oils. 
Its  specific  gravity  is  1.604;  and  its  boiling-point,  76°  to  77°  C. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  Upon  evaporation  on  a  water-bath  25  c.c.  of  carbon 
tetrachloride  should  leave  no  weighable  residue.  (Indicating  less  than  0.00125 
per  cent.) 

Chlorine.  —  No  blue  color  should  appear  upon  shaking  20  c.c.  of  carbon 
tetrachloride  with  5  c.c.  of  zinc  iodide-starch  solution.  (Indicating  less  than 
0.0002  per  cent.) 

Hydrochloric  Acid.  —  After  shaking  20  c.c.  of  carbon  tetrachloride  with  10 
c.c.  of  water  about  one  minute,  the  water  should  have  a  neutral  reaction  and 
should  show  no  change  upon  addition  of  solution  of  silver  nitrate.  (Indicating 
less  than  0.0001  per  cent  Cl.) 

Organic  Matter.  —  If  20  c.c.  of  carbon  tetrachloride  with  15  c.c.  of  concentrated 
sulphuric  acid  are  frequently  shaken  in  a  glass-stoppered  flask  that  has  previously 
been  rinsed  with  sulphuric  acid,  no  color  should  appear  in  the  acid  within  one 
hour.  (Indicating  none  present.) 


*  Under  the  influence  of  light,  carbon  disulphide  becomes  yellowish,  and  then 
leaves  a  slight  residue  on  evaporation. 


CARMINE  67 


Aldehyde.  —  If  10  c.c.  of  carbon  tetrachloride  and  10  c.c.  of  solution  of  potas- 
sium hydroxide  (sp.gr.  1.3)  are  warmed  for  one  minute  with  frequent  shaking, 
neither  a  yellow  nor  a  brown  color  should  appear  in  the  potassium  hydroxide 
solution.  (Indicating  none  present.) 

Carbon  Bisulphide.  —  Allow  a  mixture  of  10  c.c.  of  carbon  tetrachloride  and 
10  c.c.  of  a  solution  of  10  gm.  of  potassium  hydroxide  in  100  gm.  of  absolute 
alcohol  to  stand  about  one  hour.  The  subsequent  addition  to  this  of  5  c.c.  of 
dilute  acetic  acid  (sp.gr.  1.040-1.042)  and  some  solution  of  copper  sulphate 
should  not  develop  a  yellow  precipitate  within  two  hours.  (Indicating  less 
than  0.02  per  cent  CS2.) 

NOTE.  —  Regarding  the  quantitative  determination  of  carbon  disulphide 
in  carbon  tetrachloride  see  W.  Schmitz-Dumont,  Chem.  Ztg.,  21,  487,  510 
(1897);  abst.,  J.  Chem.  Soc.,  74,  II,  140  (1898).  L.  G.  Radcliffe,  Z.  angew. 
Chem.,  22,  1413  (1909);  abst.,  J.  Chem.  Soc.,  96,  II,  438  (1909).  J.  Soc.  Chem. 
Ind.,  28,  229  (1909);  abst.,  J.  Chem.  Soc.,  96,  II,  438  (1909). 

CARMINE 
(Carmine  1.     [Naccarat]) 

Bright  red,  light  pieces,  which  are  easily  reduced  to  a  fine 
powder.  Carmine  is  insoluble  in  water,  and  in  dilute  acids,  but  is 

soluble  in  ammonia. 

TESTS   OF  PURITY 

Water.  —  1  gm.  of  carmine  should  not  lose  more  than  0.25  gm.  in  weight 
upon  drying  at  100°  C.  (Indicating  not  more  than  25  per  cent.) 

Solubility.  —  0.15  gm.  should  be  almost  completely  soluble  in  a  mixture  of 
5  c.c.  of  ammonia  water  and  20  c.c.  of  water,  yielding  a  violet-red  solution; 
only  a  small  amount  of  flocculent  matter  should  remain  undissolved. 

Ash.  —  0.25  gm.  of  carmine  cautiously  incinerated  in  a  porcelain  crucible 
should  not  yield  an  ash  weighing  more  than  0.020  gm.  (Indicating  not  more 
than  8  per  cent.)  Particular  attention  should  be  paid  to  the  odor  of  burning 
carmine;  it  is  similar  to  that  yielded  during  the  combustion  of  proteids.  An 
odor  of  bromine  would  point  to  a  sophistication  with  an  eosine-lake;  and  an 
odor  of  phenol  would  point  to  an  admixture  of  paeonine-lake. 

NOTE.  —  Regarding  the  adulterations  of  cochineal-carmine  see  E.  Donath, 
Dingl.  pol.  J.,  294,  188  (1894);  abst.,  J.  Soc.  Chem.  Ind.,  14,  305  (1895). 

Regarding  the  composition  of  carmine  ash  see  S.  Feitler,  Z.  angew.  Chem., 
5,  136  (1892)  [or  Z.  anal.  Chem.,  32,  627  (1893)];  abst.,  J.  Chem.  Soc.  Ind.,  12, 
256  (1893). 

Regarding  the  use  of  carmine  as  a  staining  reagent  see  Gould's  Illustrated 
Dictionary  of  Medicine.  5  ed.,  1389-1400  (1907). 

CARMINE-FIBRIN 
(Carmine-fibrin  in  Glycerol) 

Dark,  cherry-red  masses,  of  a  crumbling  nature,  and  prepared  by 
dyeing  washed  blood  fibrin  with  an  ammoniacal  solution  of  carmine, 
as  described  by  Griitzner. 


68  CHEMICAL  REAGENTS 

Carmine-fibrin  swells  up,  but  does  not  dissolve  or  yield  up  its 
coloring  matter,  when  treated  with  hydrochloric  acid  of  0.1  per  cent 
strength.  If  pepsin,  however,  is  added  to  this  acid,  the  fibrin  is 
more  or  less  dissolved,  depending  on  the  quantity  and  strength  of 
the  pepsin  and  on  the  length  of  time  allowed  for  solution  to  be  effected. 
The  progress  of  the  reaction  may  be  known  from  the  color  of  the 
liquid,  in  which  the  carmine  dissolves  as  rapidly  as  the  fibrin  is 
digested. 

Carmine-fibrin  should  be  washed  with  water  before  use,  pressed 
out  with  the  hands,  and  allowed  to  swell  up  completely  in  hydro- 
chloric acid  of  0.1-0.2  per  cent  strength.  In  the  swollen  con- 
dition it  is  cut  up  with  shears. 

r  NOTE.  —  Regarding  the  use  of  carmine-fibrin  for  the  colorimetric  valuation 
of  pepsin  see  P.  Griitzner,  Pfliiger's  Arch.  ges.  Physiol.,  452  (1874).  See  also  E. 
Merck's  Annual  Report,  46,  on  the  year  1905.  A.  Korn,  Inauguraldissertation, 
Tubingen  (1902). 

CHARCOAL,  ANIMAL 
(Blood  Charcoal,  Purified  by  Acid) 

A  dry,  light,  black  powder. 

TESTS  OF  PURITY 

Material  Soluble  in  Water.  —  Exhaust  1  gm.  of  animal  charcoal  by  boiling 
with  20  c.c.  of  water  for  about  five  minutes  under  a  reflux  condenser.  Filter 
and  evaporate  the  filtrate  to  dryness.  The  residue  should  not  weigh  more  than 
0.003  gm.  (Indicating  not  more  than  0.3  per  cent.) 

Material  Soluble  in  Alcohol.  —  Boil  a  mixture  of  2  gm.  of  animal  charcoal 
and  40  c.c.  of  alcohol  (about  85  per  cent  by  weight)  for  about  five  minutes  under 
a  reflux  condenser;  then  filter.  20  c.c.  of  the  filtrate  should  not  leave  more 
than  0.001  gm.  of  residue  on  evaporation.  (Indicating  not  more  than  0.1  per 
cent.) 

Sulphates,  Chlorides,  and  Nitrates.  —  Boil  1  gm.  of  animal  charcoal  with 
50  c.c.  of  water  for  a  few  minutes,  and  filter.  The  filtrate  should  be  colorless 
and  neutral.  On  adding  to  10  c.c.  of  the  filtrate  some  barium  nitrate  solution, 
no  immediate  turbidity  should  be  produced.  (Indicating  less  than  0.05  per  cent 
S03.)| 

On  adding  silver  nitrate  solution  to  10  c.c.  of  the  filtrate,  not  more  than  a 
slight  opalescence  should  develop.  (Indicating  less  than  0.01  per  cent  Cl.) 

On  adding  a  granule  of  sodium  chloride,  1  drop  of  1  :  1000  indigo  solution 
and  10  c.c.  of  concentrated  sulphuric  acid  to  10  c.c.  of  the  filtrate,  the  blue 
color  of  the  solution  should  not  disappear  upon  shaking.  (Indicating  less  than 
0.016  per  cent  N2O5.) 

Copper,  Iron,  and  Calcium.  —  Boil  1  gm.  of  animal  charcoal  with  40  c.c.  of 
water  and  10  c.c.  of  hydrochloric  acid  for  about  five  minutes,  filter,  and  to  10 
c.c.  of  the  filtrate  add  5  c.c.  of  ammonia  water;  the  liquid  should  not  acquire  a 
blue  color  (indicating  less  than  0.002  per  cent  Cu),  nor  should  a  flocculent  pre- 


CHLORINE  WATER  69 


cipitate  form  (indicating  less  than  0.02  per  cent  Fe).  On  the  further  addition 
of  a  few  drops  of  ammonium  oxalate  solution  no  turbidity  should  develop  imme- 
diately (indicating  less  than  0.025  per  cent  Ca.). 

Residue  on  Ignition.  —  1  gm.  of  animal  charcoal  should  leave  a  residue 
weighing  not  more  than  0.10  gm.  on  ignition.  (Indicating  not  more  than  10  per 
cent.) 

Hydrogen  Sulphide.  —  Heat  1  gm.  of  animal  charcoal  with  40  c.c.  of  water 
and  10  c.c.  of  hydrochloric  acid,  and  test  the  escaping  vapors  with  moistened 
lead  acetate  paper.  The  latter  should  not  acquire  a  brown  color.  (Indicating 
less  than  0.001  per  cent  S.) 

Decolorizing  Power.  —  Dissolve  0.2  gm.  of  Bismarck  brown  in  100  c.c.  of 
water.  Mix  0.1  gm.  of  animal  charcoal  with  40  c.c.  of  this,  boil  for  10  minutes 
under  a  reflux  condenser,  and  then  filter.  The  filtrate  should  be  nearly  colorless. 

CHLORINE  WATER 

A  clear,  pale,  greenish-yellow  liquid,  having  a  strong  odor  of 
chlorine.  The  liquid  should  contain  about  0.4  per  cent  of  Cl. 

TESTS  OF  PURITY 

Non- volatile  Matter.  —  20  gm.  of  chlorine  water  evaporated  in  a  glass  dish 
on  a  water-bath  should  leave  no  weighable  residue.  (Indicating  less  than  0.0025 
per  cent.) 

Hydrochloric  Acid.*  —  Shake  20  gm.  of  chlorine  water  with  about  5  gm.  of 
pure  mercury  vigorously  for  five  minutes.  Filter,  add  phenolphthalein  to  the 
filtrate,  and  run  in  normal  potassium  hydroxide  solution,  by  drops,  until  a 
red  color  appears.  Not  more  than  0.1  c.c.  of  normal  alkali  should  be  required 
to  produce  the  red  end-point.  (Indicating  less  than  0.018  per  cent  HC1.) 

Chlorine  Content.  —  Let  25  gm.  of  chlorine  water  run  into  a  flask  containing 
a  solution  of  1  gm.  of  potassium  iodide  in  25  c.c.  of  water.  Add  a  few  drops  of 
starch  solution,  and  titrate  the  liberated  iodine  with  decinormal  sodium  thiosul- 
phate  solution,  of  which  at  least  28.2  c.c.  should  be  used  to  cause  the  blue  color 
to  disappear. 

1  c.c.  of  decinormal  Na2S2O3  =  0.003546  gm.  of  Cl,  log.  54974. 

CHLOROFORM 
CHC13.    Mol.  Wt.  119.39 

A  clear,  colorless,  very  volatile  liquid,  slightly  soluble  in  water 
(1  :  200),  but  miscible  in  all  proportions  with  alcohol,  ether,  and 
fatty  and  volatile  oils.  Chloroform  has  a  specific  gravity  of  1.485 
to  1.489,  and  boils  at  60°  to  62°  C.f 

*  Chlorine  water,  unless  recently  prepared,  always  contains  hydrochloric  acid. 

f  The  readiness  of  pure  (absolute)  chloroform  to  decompose  may  be  pre- 
vented by  the  addition  of  a  small  amount  (up  to  1  per  cent)  of  pure  absolute 
alcohol.  Chloroform  of  the  above  specific  gravity  contains  about  1  per  cent  of 
alcohol.  The  alcohol  may  be  removed  by  shaking  it  with  water,  then  with  pure 
sulphuric  acid,  then  separating  the  chloroform  and  mixing  it  with  granulated 
potassium  carbonate,  and  distilling. 


70  CHEMICAL  REAGENTS 


TESTS   OF  PURITY 

Non-volatile  Matter.  —  25  c.c.  of  chloroform  upon  evaporation  on  a  water- 
bath  should  leave  no  weighable  residue.  (Indicating  less  than  0.0014  per  cent.) 

Hydrochloric  Acid.  —  Vigorously  shake  together  20  c.c.  of  chloroform  and 
10  c.c.  of  water  for  about  a  minute;  after  the  chloroform  has  separated,  draw 
off  the  aqueous  layer  with  a  pipette.  The  aqueous  liquid  should  not  redden 
blue  litmus  paper,  nor  should  it  be  changed  on  the  addition  of  silver  nitrate 
solution.  (Indicating  less  than  0.0001  per  cent  HC1.) 

Free  Chlorine.  —  On  shaking  20  c.c.  of  chloroform  with  5  c.c.  of  zinc  iodide- 
starch  solution,  the  latter  should  not  acquire  a  blue  color.  (Indicating  less 
than  0.0002  per  cent  Cl.) 

Phosgen.  —  If  10  c.c.  of  chloroform  are  overlaid  with  clear  baryta  water, 
no  white  film  should  form  at  the  contact-surfaces  of  the  two  liquids.  (Indicating 
none  present.) 

Aldehyde.  —  10  c.c.  of  chloroform  and  10  c.c.  of  solution  of  potassium 
hydroxide  (sp.gr.  1.3)  are  warmed  for  one  minute  while  vigorously  stirred. 
Neither  a  brown  nor  yellow  color  should  appear  in  the  potassium  hydroxide 
solution.  (Indicating  none  present.) 

Foreign  Organic  Bodies.  —  On  repeatedly  shaking  20  c.c.  of  chloroform, 
15  c.c.  of  concentrated  sulphuric  acid,  and  4  drops' of  formaldehyde,  in  a  glass- 
stoppered  flask,  which  has  been  rinsed  previously  with  sulphuric  acid,  the  acid 
should  not  acquire  a  color  within  one-half  hour.  (Indicating  none  present.) 

CHROMIUM    TRIOXIDE    FOR    CARBON    DETERMINATION 

(Acid  Chromic  for  Carbon  Determination) 
CrO3.    Mol.  Wt.  100.1 

Dark,  brownish-red,  hygroscopic  needles  or  rhombic  prisms, 
which  are  very  easily  soluble  in  water.  The  preparation  contains 
at  least  80  per  cent  of  CrOs. 

TESTS   OF  PURITY 

Carbon.  —  This  test  is  to  be  carried  out  as  described  by  Lunge,  [Chem.-tech. 
Untersuch.-Meth.,  5  ed.,  2,  56  (1904)j  in  his  Estimation  of  Carbon  in  Iron  by 
Combustion  in  the  Wet  Way.  For  the  test  use  a  solution  of  15  gm.  of  chromium 
trioxide  in  150  c.c.  of  water  and  200  c.c.  of  concentrated  sulphuric  acid  (sp.gr. 
1.84).  The  use  of  a  wash  bottle  of  concentrated  sulphuric  acid  between  the  com- 
bustion tube  and  the  U-tube  of  glacial  phosphoric  acid  is  recommended. 

Quantitative  Determination.  —  This  test  is  to  be  made  in  the  manner  described 
under  Chromium  Trioxide,  Free  from  Sulphuric  Acid. 

CHROMIUM   TRIOXIDE,   FREE   FROM   SULPHURIC   ACID 

([Acid]  Chromic  Anhydride) 
CrO3.    Mol.  Wt.  100 

Dark,  brownish-red,  hygroscopic  needles,  or  rhombic  prisms, 
very  readily  soluble  in  water.  Chromium  trioxide  contains  almost 
100  per  cent  of  CrO3. 


COBALT  NITRATE  71 


TESTS  OF  PURITY 

Sulphuric  Acid.  —  10  gm.  of  chromium  trioxide  must  afford  a  clear  solution 
jvith  100  c.c.  of  water.  On  adding  to  the  solution  20  c.c.  of  hydrochloric  acid 
and  some  barium  chloride  solution,  no  turbidity  should  occur  within  fifteen  hours. 
(Indicating  less  than  0.005  per  cent  SO3.) 

Potassium  Sulphate  and  Potassium  Chromate.  —  Ignite  0.2  gm.  of  chromium 
trioxide  in  a  porcelain  crucible,  triturate  the  residue  with  about  20  c.c.  of  water, 
and  filter.  Evaporate  the  filtrate  to  dryness  on  -a  water-bath,  dry  the  residue 
at  100°  C.,  and  weigh.  The  residue  must  not  weigh  more  than  0.002  gm.  (Indi- 
cating not  more  than  1  per  cent.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  chromium  trioxide  in  water 
and  dilute  to  100  c.c.  Introduce  10  c.c.  of  this  solution  into  a  stoppered  flask 
of  about  400  c.c.  capacity,  dilute  with  100  c.c.  of  water,  and  add. 5  gm.  of  potas- 
sium iodide  and  2  c.c.  of  hydrochloric  acid.  Allow  the  mixture  to  stand  for  about 
ten  minutes  with  frequent  shaking,  then  dilute  with  200  c.c.  of  water,  and  titrate 
with  decinormal  sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3=  0.003333  gm.  of  CrO3,  log.  52288. 


COBALT    NITRATE 

(Cobaltous  Nitrate) 
Co(NO3)2+6H2O.    Mol.  Wt.  291.09 

Red,  monoclinic  prisms,  deliquescent  in  moist  air,  and  readily 
soluble  in  water  and  alcohol. 


COBALT   NITRATE 

TESTS   OF  PURITY 

Sulphates.  —  A  solution  of  1  gm.  of  cobalt  nitrate  in  20  c.c.  of  water,  to 
which  have  been  added  1  c.c.  of  hydrochloric  acid  and  a  little  barium  chloride 
solution,  should  not  become  turbid.  (Indicating  less  than  0.01  per  cent  SO3.) 

Chlorides.  —  The  1  :  20  aqueous  solution,  acidulated  with  nitric  acid,  should 
show  at  most  a  faint  opalescence  upon  addition  of  silver  nitrate  solution.  (Indi- 
cating less  than  0.002  per  cent  Cl.) 

Alkali  Salts.  —  Precipitate  the  cobalt  completely  from  a  solution  of  2  gm. 
of  cobalt  nitrate  in  100  c.c.  of  water  by  adding  ammonia  water  and  ammonium 
sulphide  solution;  filter,  evaporate  the  filtrate  to  dryness,  and  ignite  the  residue. 
The  weight  of  the  latter  should  not  exceed  0.005  gm.  (Indicating  not  more  than 
0.25  per  cent.) 

Zinc.  —  To  a  solution  of  0.5  gm.  of  cobalt  nitrate  in  50  c.c.  of  water,  add  5 
c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3);  filter,  and  to  the  filtrate  add 
ammonium  sulphide  solution.  No  precipitate  should  form.  (Indicating  less 
than  0.5  per  cent  Zn.) 

Lead  and  Copper.  —  Dissolve  2  gm.  of  cobalt  nitrate  in  50  c.c.  of  water, 
and  add  2  c.c.  of  nitric  acid,  followed  by  hydrogen  sulphide  water.  The  solution 
must  show  no  change.  (Indicating  less  than  0.02  per  cent  Pb,  or  less  than  0.002 
per  cent  Cu.) 


72  CHEMICAL  REAGENTS 

II 
COBALT  NITRATE,  FREE  FROM  NICKEL 

TESTS  OF  PURITY 

Nickel.  —  To  a  solution  of  1  gm.  of  cobalt  nitrate  in  20  c.c.  of  watei  add  1.5 
gm.  of  potassium  cyanide  and  heat  until  a  yellow  color  develops.  Filter,  cool, 
add  1  c.c.  of  bromine,  and  shake  until  the  bromine  is  dissolved.  The  subsequent 
addition  of  10  c.c.  of  solution  of  sodium  hydroxide  (sp.gr.  1.168  to  1.172) 
should  not  cause  a  black  precipitate.  (Indicating  less  than  0.02  per  cent  Ni.) 

The  tests  for  sulphates,  chlorides,  alkali  salts,  zinc,  lead,  and  copper  are  also 
to  be  made,  as  described  and  conditioned  under  Cobalt  Nitrate,  page  71. 

COBALT  OXIDE 
Co203.    Mol.  Wt.  165.94 

A  fine,  black  powder  free  from  sulphur.  It  is  used  to  deter- 
mine sulphur  in  coal  and  coke  according  to  the  method  of 

Brunck.* 

TEST  OF  PURITY 

Sulphur.  —  Mix  5  gm.  of  cobalt  oxide  and  2.5  gm.  of  anhydrous  sodium 
carbonate  in  a  mortar  and  then  ignite  the  mixture  in  a  platinum  crucible. f  The 
melt  is  leached  with  about  50  c.c.  of  hot  water,  the  solution  filtered,  and,  after 
acidulation  with  hydrochloric  acid,  is  treated  with  solution  of  barium  chloride. 
No  precipitate  of  barium  sulphate  should  be  visible  after  standing  fifteen  hours. 
(Indicating  less  than  0.0006  per  cent  S.) 

COLLODION 

A  colorless,  or  slightly  yellowish,  neutral  syrupy  liquid,  which, 
exposed  in  thin  layers,  evaporates,  and  leaves  a  tough,  colorless 
film.  Collodion  contains  about  4  per  cent  of  soluble  cotton. 

TESTS  OF  PURITY 

Acids.  —  Blue  litmus  paper,  when  immersed  in  collodion,  should  not  be 
reddened  immediately.  (Indicating  none  present.) 

Determination  of  Residue.  —  Mix  10  c.c.  of  water  by  drops  and  with  con- 
stant stirring  with  10  gm.  of  collodion  and  then  evaporate  to  dryness  on  the 
water-bath.  The  residue  when  dried  at  95°  to  100°  C.  should  weigh  0.38  to 
0.40  gm.  (Indicating  3.8  to  4.0  per  cent.) 


*O,  Brunck,  Z.  angew.  Chem.,  18,  1560  (1905)  \abst.,  J.  Chem.  Soc.,  88,  II, 
762  (1905). 

f  In  order  to  prevent  the  alkaline  contents  of  the  crucible  from  taking  up 
sulphur  from  the  flame  gases,  the  crucible  is  allowed  to  rest  during  ignition  in 
a  circular  opening  in  an  asbestos  plate. 


COPPER  73 


COPPER,  BY  ELECTROLYSIS 

Cu.    Atomic  Wt.  63.57 
TESTS   OF  PURITY 

Foreign  Metals.*  —  (a)  Dissolve  10  gm.  of  copper  in  60  c.c.  of  nitric  acid 
(sp.gr.  1.3),  and  evaporate  the  solution  to  dryness  on  the  water-bath.  The 
residue  should  completely  dissolve  in  50  c.c.  of  water  and  10  c.c.  of  nitric  acid 
(sp.gr.  1.3),  yielding  a  clear  solution  (indicating  no  antimony  and  tin  present). 
To  the  solution  add  15  c.c.  of  concentrated  sulphuric  acid  (sp.gr.  1.84),  evaporate 
on  the  water-bath  as  far  as  possible,  heat  the  residue  on  a  sand-bath  until  vapors  of 
sulphuric  acid  begin  to  be  evolved,  and  take  up  the  residue  with  100  c.c.  of  water. 
No  insoluble  residue  should  remain  (indicating  no  lead  present).  On  adding  5 
c.c.  of  hydrochloric  acid  to  the  clear  solution,  no  turbidity  should  ensue  (indi- 
cating no  silver  present).  Now  add  150  c.c.  of  ammonia  water  to  the  liquid, 
allow  to  stand  three  to  four  hours  at  50  to  60°  C.,  filter  through  an  ashless  filter, 
and  wash  with  ammoniacal  water  until  perfectly  free  from  copper.  A  precipitate 
on  the  paper  at  this  point  is  removed  from  the  paper  by  dissolving  in  a  little 
hydrochloric  acid,  and  the  paper  is  washed  with  water.  The  mixed  acid  and 
washings  are  made  ammoniacal  again  and  filtered  through  the  same  paper. 
Incinerate  the  filter  with  any  precipitate  it  may  contain,  and  ignite.  The  residue 
should  not  weigh  more  than  0.001  gm.  (Indicating  not  more  than  0.01  per  cent 
iron  and  bismuth  as  Fe2O3  and  Bi2O3.) 

(6)  Dissolve  10  gm.  of  copper  in  60  c.c.  of  nitric  acid  (sp.gr.  1.3),  add  to  the 
solution  15  c.c.  of  concentrated  sulphuric  acid  (sp.gr.  1.84),  evaporate  the  solu- 
tion on  the  water-bath  as  far  as  possible,  and  heat  the  residue  on  a  sand-bath  until 
the  vapors  of  sulphuric  acid  begin  to  be  evolved.  Dissolve  the  residue  in  300  c.c. 
of  water,  pass  hydrogen  sulphide  gas  into  the  solution  at  70°  C.  until  the  copper 
is  completely  precipitated, 'filter,  concentrate  the  filtrate,  expel  the  sulphuric  acid 
on  the  sand-bath,  and  ignite  the  residue.  The  weight  of  the  latter  should  not 
exceed  0.002  gm.  (Indicating  not  more  than  0.02  per  cent.) 

Arsenic.  —  Dissolve  10  gm.  of  copper  in  60  c.c.  of  nitric  acid  (sp.gr.  1.3),  add 
to  the  solution  15  c.c.  of  concentrated  sulphuric  acid  (sp.gr.  1.84),  evaporate  the 
solution  on  the  water-bath  as  far  as  possible,  and  then  heat  the  residue  on  the 
sand-bath  until  vapors  of  sulphuric  acid  are  evolved.  When  cold,  dissolve  the 
residue  in  100  c.c.  of  water. 

Set  a  Marsh  apparatus  in  operation,  using  50  gm.  of  arsenic-free,  granulated 
zinc,  and  dilute  (1  :  5)  sulphuric  acid,  then  introduce  the  copper  sulphate  solution 
in  small  quantities  at  a  time,  and  maintain  the  flow  of  gas  for  one  hour.  No 
deposit  of  arsenic  should  be  visible  in  the  reduction  tube  within  this  time.  (Indi- 
cating less  than  0.0001  per  cent  As.) 

COPPER  CHLORIDE,  CUPRIC 

(Copper  Dichloride) 
CuCl2+2H2O.    Mol.  Wt.  170.52 
Green,  hygroscopic  crystals,  easily  soluble  in  water  and  in  alcohol. 

TESTS   OF  PURITY 
Substances  Insoluble  in  Alcohol.  —  The  solution  of  5  gm.  of  copper  chloride 


Wash  the  copper  in  diluted  hydrochloric  acid  before  using  it  in  this  test. 


74  CHEMICAL  REAGENTS 


in  5  c.c.  of  water  should  not  be  rendered  turbid  on  mixing  with~5  c.c.  of  alcohol 
(about  85  per  cent  by  weight).  (Indicating  none  present.) 

Sulphates.  —  Dissolve  1  gm.  of  copper  chloride  in  20  c.c.  of  water,  and  add 
1  c.c.  of  hydrochloric  acid,  followed  by  barium  chloride  solution.  No  turbidity 
should  ensue  within  five  minutes.  (Indicating  less  than  0.01  per  cent  SOs.) 

Salts  of  Alkali  Metals.  —  Dissolve  3  gm.  of  copper  chloride  in  100  c.c.  of  water, 
add  5  c.c.  of  hydrochloric  acid,  and  into  the  solution,  maintained  at  about  70° 
C.,  pass  hydrogen  sulphide  gas,  until  the  copper  is  completely  precipitated;  filter, 
evaporate  the  filtrate  to  dryness,  and  ignite  the  residue.  The  weight  of  the  latter 
should  not  exceed  0.002  gm.  (Indicating  not  more  than  0.066  per  cent.) 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  granulated  zinc  into  the  gen- 
erating flask  of  a  Marsh  apparatus,  and  start  the  hydrogen  by  adding  dilute 
(1  :  5)  sulphuric  acid.  Dissolve  1  gm.  of  copper  chloride  in  20  c.c.  of  water, 
introduce  the  solution  in  small  quantities  at  a  time  into  the  Marsh  apparatus, 
and  maintain  a  slow  stream  of  gas  for  one  hour.  No  deposit  of  arsenic  should 
be  visible  in  the  reduction  tube  of  the  apparatus  within  this  time.  (Indicating 
less  than  0.001  per  cent  As.) 

Iron.  —  Heat  to  boiling  a  solution  of  5  gm.  of  copper  chloride  in  25  c.c.  of 
water  containing  2  c.c.  of  nitric  acid  (sp.  gr.  1.3),  then  add  35  c.c.  of  ammonia  water. 
Filter,  and  wash  with  ammoniacal  water  until  the  copper  is  all  removed  from  the 
paper.  Any  precipitate  remaining  on  the  paper  is  dissolved  in  a  little  hydrochloric 
acid,  the  paper  washed,  and  the  acid  and  washings  after  mixing  are  treated  with 
an  excess  of  ammonia  water.  Any  precipitate  is  filtered  through  the  original 
paper.  The  paper  and  precipitate  are  ignited,  leaving  a  residue  weighing  not 
more  than  0.002  gm.  (Indicating  not  more  than  0.028  per  cent  Fe.) 


COPPER  CHLORIDE,  CUPROUS 

(Copper  Monochloride) 

Cu2Cl2.    Mol.  Wt.  198.06 

A  white,  crystalline  powder,  insoluble  in  water,  but  soluble  in 
concentrated  hydrochloric  acid  and  in  ammonia  water. 

The  quality  of  cuprous  chloride  may  be  judged  from  its  appear- 
ance.    The  preparation  should  be  white,  but  not  green  or  brown.* 
Both  the  hydrochloric  acid  and  the  ammoniacal  solutions  should 
rapidly  and  freely  absorb  carbon  monoxide. 

COPPER  HYDROXIDE 

Light  blue  paste  prepared  according  to  Fassbender's  method.f 


*  Cuprous  chloride  soon  acquires  a  green  color  in  air. 

t  G.  Fassbender,  Ber.,  13,  1821  (1880);  abst.,  J.  Chem.  Soc.,  40,  205  (1881). 
See  also  A.  Stutzer,  Ber.,  13,  251  (1880);  dbst.,  J.  Chem.  Soc.,  38,  676  (1880); 
Chem.  Ztg.,  4,  360  (1880)  [or  Z.  anal.  Chem.,  20,  307  (1880)];  dbst.,  J.  Chem. 
Soc.,  40,  660  (1881).  E.  Schulze  and  J.  Barbieri,  Landw.  Vers.  Sta.,  26,  213-283 
[orZ.  Anal.  Chem.,  20,  588  (1881)];  abst.,  J.  Chem.  Soc.,  40,  312  (1881). 


COPPER  OXIDE  75 


TEST   OF  PURITY 

Sulphates,  Alkalies.  —  Shake  50  c.c.  of  water  with  10  gm.  of  the  copper 
hydroxide  and  then  filter.  The  filtrate  should  be  neutral  (indicating  no  free 
alkalies  present)  and  show  no  change  upon  the  addition  of  solution  of  barium 
chloride.  (Indicating  less  than  0.001  per  cent  SO3.) 

COPPER    OXIDE 

(Cupric  Oxide) 
CuO.    Mol.  Wt.  79.57 

Copper  oxide  is  used  in  ultimate  organic  analysis,  in  the  form 
of  fine  powder  or  coarse  granules,  and  also  in  the  form  of  wire. 


COPPER  OXIDE,   POWDER 

A  black  powder. 

TESTS  OF  PURITY 

Nitrates  and  Carbon  Dioxide.  —  On  heating  100  gm.  of  copper  oxide  in  a  glass 
tube,  and  passing  over  it  a  stream  of  moist  air  freed  from  carbonic  acid,  no  vapors 
should  be  given  off  which  redden  litmus  paper,  or  render  lime-water  turbid. 
(Indicating  none  present.) 

Chlorides.  —  The  solution  of  1  gm.  of  copper  oxide  in  10  c.c.  of  nitric  acid 
and  10  c.c.  of  water  should  not  be  rendered  cloudy  by  silver  nitrate  solution. 
(Indicating  less  than  0.0005  per  cent  Cl.) 

Substances  not  Precipitated  by  Hydrogen  Sulphide  (Iron,  Insoluble  Matter, 
etc.).  —  Dissolve  2  gm.  of  copper  oxide  in  10  c.c.  of  hydrochloric  acid  (sp.gr.  1.19), 
dilute  with  water  to  100  c.c.;  ignite  the  insoluble  residue,  the  weight  of  which 
should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.05  per  cent  insoluble 
matter.)  Pass  hydrogen  sulphide  gas  into  the  solution  at  about  70°  C.,  until 
the  copper  has  completely  precipitated,  filter,  evaporate  the  filtrate  on  the  water- 
bath,  and  ignite  the  residue.  The  weight  of  the  latter  should  not  exceed  0.005 
gm.  (Indicating  not  more  than  0.25  per  cent.) 

Soluble  Substances  (Alkali  Salts,  etc.).  —  Shake  3  gm.  of  copper  oxide  with 
60  c.c.  of  water  a  few  minutes  and  then  filter.  The  filtrate  should  not  react 
alkaline  with  litmus,  and  upon  evaporation  and  ignition  should  leave  no  weighable 
residue.  (Indicating  less  than  0.0167  per  cent.) 

Sulphates.  — •  Dissolve  1  gm.  of  copper  oxide  in  5  c.c.  of  hydrochloric  acid 
(sp.gr.  1.19),  dilute  with  20  c.c.  water  and  add  barium  chloride  solution.  No 
change  should  appear.  (Indicating  less  than  0.08  per  cent  SOs.) 

Calcium.  —  Digest  20  gm.  of  copper  oxide  with  a  mixture  of  5  c.c.  of  nitric 
acid  and  95  c.c.  of  water  for  about  fifteen  minutes,  shaking  frequently,  filter, 
precipitate  the  copper  in  the  filtrate  completely  by  passing  hydrogen  sulphide 
gas,  and  filter  again.  Evaporate  the  filtrate  on  the  water-bath  to  about  20 
c.c.,  add  ammonia  water  in  excess,  filter  once  more,  and  to  the  filtrate  add 
ammonium  oxalate  solution.  No  immediate  turbidity  should  be  produced. 
(Indicating  less  than  0.00125  per  cent  Ca.) 


76  CHEMICAL  REAGENTS 

II 
COPPER  OXIDE,    GRANULAR 

Grayish-black  granules. 

TESTS  OF  PURITY 

The  tests  for  nitrates,  carbon  dioxide,  and  calcium  are  to  be  made  as  described 
under  copper  oxide,  powder.  The  granules  are  to  be  powdered  before  testing. 

Sulphates.  —  Dissolve  1  gm.  of  granulated  copper  oxide  in  5  c.c.  of  hydro- 
chloric acid  (sp.gr.  1.19),  dilute  with  20  c.c.  of  water  and  filter.  The  filtrate 
should  become  at  most  slightly  opalescent  upon  the  addition  of  barium  chloride 
solution.  (Indicating  less  than  0.1  per  cent  SO3.) 

Chlorides.  —  1  gm.  of  granulated  copper  oxide  is  powdered  and  shaken  a 
few  minutes  with  10  c.c.  of  nitric  acid  and  10  c.c.  of  water.  After  filtering,  silver 
nitrate  solution  should  not  produce  a  cloud  in  the  filtrate.  (Indicating  less  than 
0.005  per  cent  Cl.) 

Ill 
COPPER   OXIDE,  WIRE 

This  occurs  in  the  form  of  short  cylindrical  pieces. 

COPPER  SULPHATE 

(Cupric  Sulphate) 
CuSO4+sH2O.    Mol.  Wt.  249.72 

Blue,  transparent  crystals,  slightly  efflorescent  in  dry  air,  soluble 
in  3.5  parts  of  cold,  and  in  1  part  of  boiling,  water;  almost  insoluble 
in  alcohol.  The  aqueous  solution  is  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Salts  of  the  Alkalies,  Earths,  etc.  —  Dissolve  3  gm.  of  copper  sulphate  in  100 
c.c.  of  water,  add  5  c.c.  of  hydrochloric  acid,  and  into  the  solution,  maintained 
at  about  70°  C.,  pass  hydrogen  sulphide  gas  until  the  copper  is  completely  pre- 
cipitated. On  evaporating  the  filtrate  to  dryness,  and  igniting  the  residue,  the 
weight  of  the  latter  should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.033 
per  cent.) 

Iron.  —  To  the  solution  of  5  gm.  of  copper  sulphate  in  25  c.c.  of  water,  add 
2  c.c.  of  nitric  acid  (sp.gr.  1.3),  and  heat  the  mixture  to  boiling.  Then  add  20 
c.c.  of  ammonia  water,  pour  the  liquid  through  an  ashless  filter,  and  wash  the 
latter  with  ammoniacal  water  until  perfectly  free  from  copper.  Any  precipitate 
on  the  filter  paper  is  dissolved  in  a  little  hydrochloric  acid,  the  paper  washed  with 
water,  and  the  mixed  acid  and  washings  are  treated  again  with  excess  of  ammonia 
water.  Filter  through  the  same  paper.  Incinerate  and  ignite  the  filter  together 
with  any  precipitate  it  may  contain.  The  weight  of  the  residue  should  not 
exceed  0.001  gm.  (Indicating  not  more  than  0.014  per  cent  Fe.) 


COPPER  AND  AMMONIUM  CHLORIDE  77 

COPPER  AND  AMMONIUM  CHLORIDE 

(Ammonio-Cupric  Chloride) 
CuCl22NH4Cl+2H2O.     Mol.  Wt.  277.51 

Blue  crystals  soluble  in  4  parts  of  water,  yielding  a  solution 
slightly  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Free  Acids.  —  A  solution  of  30  gm.  of  copper  and  ammonium  chloride  in 
100  c.c.  of  water  must  be  perfectly  clear.  On  introducing  into  the  solution  several 
pieces  of  piano  wire,  the  latter  should  dissolve  with  the  deposition  of  copper,  but 
without  any  evolution  of  gas.  (Indicating  none  present.) 

Sulphates.  —  Dissolve  1  gm.  of  copper  and  ammonium  chloride  in  20  c.c.  of 
water,  and  add  1  c.c.  of  hydrochloric  acid,  followed  by  barium  chloride  solution. 
No  turbidity  should  be  produced  within  five  minutes.  (Indicating  less  than 
0.01  per  cent  SO3.) 

Salts  of  the  Alkalies,  Earths,  etc.  —  Dissolve  3  gm.  of  copper  and  ammonium 
chloride  in  about  100  c.c.  of  water,  add  5  c.c.  of  hydrochloric  acid,  pass  hydrogen 
sulphide  gas  into  the  solution  at  about  70°  C.,  until  the  copper  is  completely 
precipitated;  filter,  evaporate  the  filtrate,  and  ignite  the  residue.  The  weight 
of  the  latter  should  not  exceed  0.002  gm.  (Indicating  not  more  than  0.067  per 
cent.) . 

Iron.  —  Dissolve  5  gm.  of  copper  and  ammonium  chloride  in  25  c.c.  of  water, 
add  2  c.c.  of  nitric  acid  (sp.gr.  1.3),  heat  to  boiling,  then  add  20  c.c.  of  ammonia 
water  and  pour  the  liquid  through  an  ashless  filter.  Wash  the  latter  with  ammo- 
niacal  water  until  perfectly  free  from  copper,  dissolve  any  precipitate  on  the 
paper  with  hydrochloric  acid,  wash  the  paper  with  water,  and  then  add  an  excess 
of  ammonia  water  to  the  mixed  hydrochloric  acid  and  washings.  Filter  through 
the  same  paper,  and  then  incinerate  and  ignite  the  filter  together  with  any  pre- 
cipitate it  may  contain.  The  weight  of  the  residue  should  not  exceed  0.001  gm. 
(Indicating  not  more  than  0.014  per  cent  Fe.) 

DEVARDA'S  METAL 
(Devarda's  Alloy) 

Devarda's  metal  is  a  gray  powder  composed  of  50  parts  of  copper, 
45  parts  of  aluminum,  and  5  parts  of  zinc.  The  powder  is  partly 
soluble  in  hydrochloric  acid,  copper  separating  out. 

TEST  OF  PURITY 

Nitrogen.  —  Place  10  gm.  of  Devarda's  metal  in  an  Erlenmeyer  flask  of  about 
1  liter  capacity,  add  100  c.c.  of  hydrochloric  acid,  and  allow  to  stand  with  frequent 
agitation  until  hydrogen  ceases  to  be  evolved.  After  cooling  add  100  c.c.  of 
nitrogen-free  solution  of  sodium  hydroxide  (sp.gr.  1.3)  and  distil  about  50  c.c., 
receiving  the  distillate  in  2  to  3  c.c.  of  fifth-normal  solution  of  hydrochloric  acid 
diluted  with  10  c.c.  of  water.  Titrate  the  distillate  with  fifth-normal  solution 
of  potassium  h  droxide,  using  methyl .  orange  as  indicator.  The  ammonia  from 


78  CHEMICAL  REAGENTS 


the  metal  should  not  consume  more  than  0.2  c.c.  of  fifth-normal  solution  of 
hydrochloric  acid.     (Indicating  not  more  than  0.0056  per  cent  N.) 

NOTE.  —  Regarding  the  use  of  Devarda's  metal  for  the  estimation  of  nitrogen 
see  A.  Devarda,  Chem.  Ztg.,  16,  1952  (1892);  abst.,  J.  Chem.  Soc.,  64,  343  (1893). 
Osterr.-Ungar.  Z.  Zucker-Ind.,  1897;  abst.,  J.  Chem.  Soc.,  74,  II,  350  (1898). 
Meissl,  Landwirtsch.  Versuchsta.,  42,  97  (1893);  dbst.,  Z.  anal.  Chem.,  33,  113 
(1894).  Compare  G.  Lunge,  Chem.-Tech.  Uhtersuch.  Meth.,  6  ed,  3,  11  .(1911). 

DICYANDIAMIDINE   SULPHATE 
(C2OH6N4)2H2SO4+2H2O.    Mol.  Wt.  338.29 

A  white  powder,  soluble  in  about  20  parts  of  cold,  and  in  about 
3  parts  of  boiling,  water. 

TEST  OF  PURITY 

Suitability  as  a  Reagent  for  Nickel. — Mix  10  c.c.  of  a  solution  of  cobalt-free 
nickel  chloride  (2.4  gm.  of  NiCl2+6H2O  in  100  c.c.  of  water)  with  3  c.c.  of  solu- 
tion of  ammonium  chloride,  10  c.c.  of  20  per  cent  ammonia  water,  and  10  c.c. 
of  solution  of  dicyandiamidine  sulphate  (4.5  gm.  in  125  c.c.  of  water).  Add  to 
this  mixture,  while  constantly  stirring,  6  c.c.  of  solution  of  potassium  hydroxide 
(sp.gr.  1.138-1.140),  allow  to  stand  about  fifteen  hours,  and  then  filter.  The 
filtrate,  to  which  10  c.c.  of  dicyandiamidine  sulphate  solution  have  been  added, 
and  which  has  then  been  allowed  to  stand  six  hours,  should  not  exhibit  a  yellow 
precipitate. 

NOTE.  —  Regarding  the  use  of  dicyandiamidine  sulphate  for  the  detection 
and  quantitative  determination  of  nickel,  as  well  as  for  its  separation  from  cobalt 
and  other  metals,  see  H.  Grossman  and  B.  Schiick,  Ber.,  39,  3356  (1906):  abst., 
J.  Chem.  Soc.,  90,  II,  903  (1906).  Chem.-Ztg.,  31,  535,  911  (1907);  abst.,  J. 
Chem.  Soc.,  92,  II,  819  (1907).  H.  Grossman  and  W.  Heilborn,  Ber.,  41,  1878 
(1908);  abst.,  J.  Chem.  Soc.,  94,  II,  635  (1908).  Chem.-Ztg., .33, 841,  851  (1909); 
dbst.,  C.  A.,  3,  2782  (1909). 

DIMETHYLGLYOXIME 

(Diacetyl-dioxime) 
CH3C(NOH)C(NOH)CH3.    Mol.  Wt.  116.08 

White,  needle-shaped  crystals  almost  insoluble  in  cold  water 
and  very  difficultly  soluble  in  boiling  water.  Difficultly  soluble  also 
in  alcohol  and  in  ether.  Dimethylglyoxime  melts  at  241°  C.,  but 
with  a  brown  discoloration. 

TEST   OF  PURITY 

Suitability  as  a  Reagent  for  Nickel. — Dissolve  2.4  gm.  of  cobalt-free  nickel 
chloride  (NiCl2+6H2O)  in  100  c.c.  of  water,  draw  off  10  c.c.  of  this  solution 
and,  after  diluting  with  100  c.c.  of  water,  heat  to  boiling  and  add  a  solution  of 
0.25  gm.  of  dimethylglyoxime  in  25  c.c.  of  alcohol  (about  85  per  cent  by  weight). 
Add  ammonia  water  by  drops  until  the  solution  is  alkaline,  and,  after  cooling, 


DIMETHYL  PARAPHENYLENEDIAMINE  HYDROCHLORIDE     79 


filter.  The  filtrate,  when  heated  to  boiling  with  alcoholic  solution  of  dimethyl- 
glyoxime  (1  :  100),  should  show  no  brown  color,  and,  upon  subsequent  cooling, 
should  exhibit  no  red  precipitate. 

NOTE.  —  Regarding  the  use  of  dimethylglyoxime  for  the  detection  and 
quantitative  determination  of  nickel  see  O.  Brunck,  Z.  angew.  Chem.,  20,  834 
(1907);a6s«.,  J.  Chem.  Soc.,  92,  II,  582  (1907).  Z.  angew.  Chem.,  20,  1844  (1907); 
abst.,  J.  Chem.  Soc.,  92,  II,  989  (1907).  P.  Bogolubow,  Stahl  u.  Eisen,  30,  458 
(1910):  abst.,  Chem.  Zentr.  (5)  14,  1643  (1910);  abst.,  C.  A.,  5,  1572  (1911).  L. 
Tschugaeff,  Ber.,  28,  2520  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  613  (1905). 
K.  Kraut,  Z.  angew.  Chem.,  19,  1793  (1906);  abst.t  J.  Chem.  Soc.,  90,  II,  858 
(1906). 

DIMETHYLPARAPHENYLENEDIAMINE  HYDROCHLORIDE 

(Para-aminodimethylaniline  Hydrochloride) 

C6H4(NH2)N(CH3)2+2HC1.     Mol.  Wt.  209.05 

A  white,  or  grayish,  hygroscopic,  crystalline  powder,  easily 
soluble  in  water,  but  less  soluble  in  alcohol.  The  article  must  be 
protected  from  air  and  moisture. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  1  gm.  of  dimethylparaphenylenediamine  hydro- 
chloride  upon  ignition  should  not  leave  a  weighable  residue.  (Indicating  less 
than  0.05  per  cent.) 

Quantitative  Determination.  —  Titrate  the  solution  of  0.5  gm.  of  dimethyl- 
paraphenylenediamine hydrochloride  in  50  c.c.  of  alcohol  (about  85  per  cent  by 
weight)  in  a  glass-stoppered  flask,  using  fifth-normal  solution  of  potassium 
hydroxide,  and  Poirrier's  blue  as  indicator. 

1  c.c.  of  fifth-normal  potassium  hydroxide  solution  =0.020905  gm.  of 
C6H4(NH2)A(CH3)  +2HC1,  log.  32025. 

NOTE.  —  Regarding  the  use  of  dimethylparaphenylenediamine  hydrochloride 
as  a  reagent  see  A.  Jolles,  Detection  of  Bromine  in  Urine,  Z.  anal.  Chem.,  37, 
439  (1898);  abst.,  J.  Chem.  Soc.,  74,  II,  637  (1898).  H.  N.  Malerba,  Detection 
of  Acetone,  Ann.  Chim.  Farm.,  21,  14  (1895);  abst.,  Chem.  Ztg.,  19,  Repert.,  82 
(1895);  abst.,  J.  Soc.  Chem.  Ind.,  14,  599  (1895).  M.  Pabst,  Reagent  for  Olive 
Pits  in  Powdered  Pepper,  Chem.  Zentr.,  (4)  11,  1074  (1890);  abst.,  J.  Soc.  Chem. 
Ind.,  9,  770  (1890).  C.  Wurster,  Quantitative  Estimation  of  Wood  in  Paper, 
Ber.,  20,  808  (1887);  abst..  J.  Chem.  Soc.,  52,  620  (1887).  C.  Wurster,  Reagent 
for  Detecting  Minimal  Quantities  of  Active  Oxygen,  Ber.,  19,  3195  (1887)  and 
21,  921  (1888);  abst.t  J.  Chem.  Soc.,  52,  295  (1887)  and  54,  627  (1888). 

DIPHENYLAMINE* 

(C6H6)2NH.    Mol.  Wt.  169.10 

White,  monoclinic  crystals,  insoluble  in  water,  but  easily  soluble 


*  The  diphenylamine  solution,  used  as  a  reagent  for  nitric  acid,  is  prepared 
by  dissolving  0.5  gm.  of  diphenylamine  in  100  c.c.  of  pure,  concentrated  sulphuric 
acid  (free  from  nitric  acid)  and  20  c.c.  of  water.  According  to  G.  Lunge  [Z. 


80  CHEMICAL  REAGENTS 

in  alcohol,  ether,  and  benzene.    Diphenylamine  melts  at  53°  C., 
and  boils  at  302°  C. 

TESTS   OF  PURITY 

Nitric  Acid.  —  0.2  gin.  of  diphenylamine  should  dissolve  in  20  c.c.  of  pure 
concentrated  sulphuric  acid  with  2  c.c.  of  water,  and  yield  a  colorless  solution. 
(Indicating  less  than  0.05  per  cent  N2O6.)  Should  a  blue  color  develop,  the  sul- 
phuric acid  should  be  tested  with  brucine  for  the  possible  presence  of  nitric  acid. 

Aniline.  —  On  pouring  1  gm.  of  powdered  diphenylamine  into  20  c.c.  of  a 
chlorinated  lime  solution,  the  liquid  should  not  acquire  a  violet  color.  (Indicating 
less  than  0.05  per  cent.) 

ETHER 

(Ethyl  Ether) 
(C2H5)2O.    Mol.  Wt.  74.08 

I 
ETHER,  Sp.Gr.  0.720 

A  clear,  colorless,  mobile  liquid  of  specific  gravity  0.720,*  boiling 
at  34°  to  36°  C.  Ether  should  not  redden  moist  blue  litmus  paper. 
Filter  paper  which  has  been  moistened  with  ether  should  have  no 
odor  when  dry. 

TESTS  OF  PURITY 

Residue.  —  On  allowing  20  c.c.  of  ether  to  evaporate  spontaneously  in  a 
glass  dish  covered  with  a  funnel,  the  residue  must  have  no  odor,  and  should  not 
redden  or  decolorize  blue  litmus  paper;  and  it  must  be  completely  volatilized 
on  warming  on  the  water-bath.  (Indicating  none  present.) 

Ethyl  Peroxide,  Hydrogen  Peroxide,  and  Ozone.  —  On  vigorously  shaking 
10  c.c.  of  ether  with  1  c.c.  of  1  :  10  aqueous  potassium  iodide  solution  in  a  com- 
pletely filled  glass-stoppered  bottle,  neither  the  ether  nor  the  potassium  iodide 
solution  should  acquire  a  color  after  standing  one  hour  in  the  dark.  (Indicating 
none  present.) 

Aldehydes  and  Vinyl  Alcohol.  —  Upon  shaking  20  c.c.  of  ether  and  5  c.c.  of 
Nessler's  solution  one  minute  in  a  glass-stoppered  flask,  neither  a  reddish-brown 
nor  a  black  precipitate  should  appear.  (Indicating  none  present.) 

Sulphur  Compounds.  —  On  shaking  20  c.c.  of  ether  with  a  globule  of  mercury 


angew.  Chem.,  7,  345  (1894);  abst.,  J.  Chem.  Soc.,  66,  II,  398  (1894)],  the  reagent 
is  employed  as  follows: 

To  test  for  nitric  or  nitrous  acid,  introduce  about  5  c.c.  of  the  reagent  solution 
into  a  test-tube,  and  overlay  it  with  the  liquid  to  be  examined.  If  the  latter  is 
specifically  heavier  than  the  reagent  solution,  the  diphenylamine  solution  is  to  be 
overlaid  upon  the  liquid. 

Regarding  the  increased  sensitiveness  of  the  nitric-acid  reaction  with  diphenyl- 
amine in  water  analysis,  see  R.  Cimmino,  Z.  anal.  Chem.  38,  429  (1899);  abst., 
J.  Chem.  Soc.,  70,  II,  805  (1899). 

*  Ether  eagerly  abstracts  moisture  from  the  atmosphere,  whereby  its  specific 
gravity  is  increased. 


ETHER  81 

for  two  minutes  in  a  glass-stoppered  bottle,  the  bright  surface  of  the  metal  must 
not  be  changed;  nor  should  a  black  precipitate  form.  (Indicating  none  present.) 

Acetone.  —  Mix  6  c.c.  of  baryta  water  and  6  drops  of  solution  of  mercuric 
chloride  (1  :  20)  with  20  c.c.  of  ether  for  one  minute.  Allow  the  liquids  to 
separate,  filter  the  aqueous  portion,  and  to  the  clear  filtrate  add  solution  of  ammo- 
nium sulphide.  No  dark  color  should  appear  within  ten  minutes.  (Indicating 
less  than  0.005  per  cent.) 

Water.  —  On  shaking  20  c.c.  of  ether  in  a  stoppered  flask  with  1  gm.  of 
anhydrous  copper  sulphate,  the  latter  should  not  acquire  a  green  or  blue  color. 
(Indicating  less  than  1%.) 

II 

ETHER,   ANHYDROUS,   DISTILLED   OVER  SODIUM 

TESTS   OF  PURITY 

In  addition  to  the  tests  given  above,  this  preparation  must  answer  the 
following  requirement : 

Water  and  Alcohol. — On  introducing  15  c.c.  of  ether  into  a  dry,  glass-stoppered 
flask  with  a  freshly-cut  piece  of  sodium  the  size  of  a  pea,  only  a  slight  evolution 
of  gas  should  take  place,  and  the  bright  metallic  surfaces  of  the  sodium  should 
not  completely  lose  their  luster  within  six  hours.  (Indicating  less  than  0.1  per 
cent  water  and  less  than  0.3  per  cent  alcohol.) 


FURFURAL 

(Furfurol) 
C6H4O2.    Mol.  Wt.  96.03 

When  freshly  prepared,  furfural  is  a  clear,  colorless  liquid;  it 
rapidly  acquires  a  yellow  color  on  exposure  to  light  and  air.  Furfural 
has  a  specific  gravity  of  1.165  to  1.166,  boils  at  158°  to  160°  C.,  and 
is  soluble  in  15  parts  of  cold  water.  It  is  very  easily  soluble  in 
alcohol  and  in  ether. 

NOTE.  —  Regarding  the  quantitative  determination  of  furfural,  see  W.  E. 
Stone,  Z.  anal.  Chem.,  40,  550  (1901);  abst.,  J.  Anal.  Appl.  Chem.,  5,  421  (1895). 
W.  Cormack,  Z.  anal.  Chem.,  43,  256  (1904);  abst.,  J.  Chem.  Soc.,  77,  990  (1900). 
Regarding  the  use  of  furfural:  (1)  As  a  reagent  for  sesame  oil,  see  F.  Utz,  Pharm. 
Ztg.,  45,  490  (1900);  abst.,  J.  Chem.  Soc.,  78,  II,  699  (1900);  also  see  Lewkowitsch, 
Chem.  Technol.  and  Anal.  Oils,  Fats,  and  Waxes,  3  ed.,  Vol.  II,  p.  542  (1904).  (2) 
As  a  reagent  for  alkaloids,  see  N.  Wender,  Chem.  Ztg.,  17,  950  (1893);  abst.,  J. 
Chem.  Soc.,  66,  II,  76  (1894);  Woltering,  Pharm.  Ztschr.  f.  Russl.,  31,  or  526  (Z. 
anal.  Chem.,  36, 410  (1897) .  (3)  As  a  reagent  for  urea,  see  H.  Schiff,  J.  Chem.  Soc., 
52,  571  (1887).  (4)  As  a  reagent  for  fusel  oil  in  alcohol,  see  A.  Komarowsky, 
Chem.  Ztg.,  27,  808  (1903);  abst.,  J.  Chem.  Soc.,  84,  II,  700  (1903).  (5)  As  a 
reagent  for  mineral  acids,  see  O.  Carletti,  Boll.  Chim.  Farm.,  45,  449;  abst.. 
C.  A.,  I.,  1458  (1907).  E.  Eggers,  Z.  anal.  Chem.,  27, 725  (1888);  abst.,  J.  Chem. 
Soc.,  56,  648  (1889). 


82  CHEMICAL  REAGENTS 

GALLEIN  DRY 

(Gallein) 

Gallein  is  a  brown  powder  soluble  in  alcohol.  It  is  used  as  an 
indicator  in  the  form  of  a  solution  of  0.5  gm.  of  gallein  dissolved  in 
a  mixture  of  50  c.c.  of  alcohol  (about  85  per  cent  by  weight)  and 
50  c.c.  of  water. 

NOTE.  —  Regarding  the  use  of  gallein  as  an  indicator,  see  H.  Dechan,  Pharm. 
J.  Trans.,  (3),  15,  849  (1885);  dbst.,  Chem.  Ztg.,  9,  715  (1885);  abst.,  J.  Ohem. 
Soc.,  48,  1012  (1885).  Compare  Bockmann,  Chem.-tech.  Untersuch.  Meth., 
3  ed.,  I,  142. 

.     GLASS  WOOL 

Glass  wool  consists  of  fine  glass  threads. 
TESTS   OF  PURITY 

Matter  Soluble  in  Hydrochloric  Acid.  —  Boil  5  gm.  of  glass  wool  a  few 
minutes  with  a  mixture  of  100  c.c.  of  hydrochloric  acid  (sp.gr.  1.124-1.126)  and 
100  c.c.  of  water.  Filter,  and  evaporate  100  c.c.  of  the  filtrate  to  dryness.  The 
residue  should  not  weigh  more  than  0.02  gm.  (Indicating  not  more  than  0.8  per 
cent.) 

Lead.  —  Boil  1  gm.  of  glass  wool  a  few  minutes  with  a  mixture  of  10  c.c. 
of  nitric  acid  (sp.gr.  1.150-1.152)  and  40  c.c.  of  water.  Filter,  evaporate  the 
filtrate  to  dryness  on  the  water-bath,  and  dissolve  the  residue  in  10  c.c.  of  water. 
After  filtering  again  the  solution  should  show  no  change  upon  the  addition  of 
hydrogen  sulphide  water.  (Indicating  less  than  0.0025  per  cent  Pb.) 

GLYCERIN 

(Glycerol) 
C3H8O3.    Mol.  Wt.  92.06 

I 
GLYCERIN,  Sp.Gr.   1.250 

A  clear,  colorless,  almost  odorless  liquid,  neutral  in  reaction, 
soluble  in  all  proportions  in  water  and  in  alcohol.  Insoluble  in  ether 
and  in  chloroform.  Specific  gravity  not  less  than  1.250.  It  contains 
at  least  95  per  cent  of  absolute  glycerin,  CsHgOa. 

TESTS   OF  PURITY 

Arsenic.  —  On  mixing  1  c.c.  of  glycerin  with  3  c.c.  of  stannous  chloride  solution 
the  mixture  should  not  darken  within  one  hour.  (Indicating  less  than  0.0012 
per  cent  As.) 


GLYCERIN  -  83 


Neutrality.  —  On  diluting  2  c.c.  of  glycerin  with  10  c.c.  of  water,  the  solution 
should  not  affect  red  or  blue  litmus  paper. 

Inorganic  Matter.  —  On  heating  5  c.c.  of  glycerin  to  boiling  in  an  open  dish 
and  then  igniting  the  vapors,  the  glycerin  should  burn  up  completely,  leaving 
only  a  dark  stain  which  should  disappear  on  being  more  strongly  heated.  No 
weighable  residue  should  remain.  (Indicating  less  than  0.008  per  cent.) 

Substances  which  Reduce  Ammoniacal  Silver  Nitrate  Solution.  —  On  heating 
a  mixture  of  1  c.c.  of  glycerin  and  1  c.c.  of  ammonia  water  on  the  water^bath 
to  60°  C.,  and  then  immediately  adding  3  drops  of  silver  nitrate  solution,  neither 
a  coloration  nor  a  brownish-black  precipitate  should  develop  within  five  minutes. 
(Indicating  none  present.) 

Hydrochloric  Acid  (Chlorides).  —  5  c.c.  of  glycerin  diluted  with  25  c.c.  of 
water  should  exhibit  at  most  a  slight,  opalescent  turbidity  on  the  addition  of 
silver  nitrate  solution.  (Indicating  less  than  0.0004  per  cent  Cl.) 

Sulphuric  and  Oxalic  Acids.  —  The  solution  of  5  c.c.  of  glycerin  in  25  c.c.  of 
water  should  not  be  affected  by  barium  chloride  solution  or  by  calcium  chloride 
solution.  (Indicating  less  than  0.0024  per  cent  SO3,  and  less  than  0.0064  per  cent 
H2C2O4). 

Heavy  Metals.  —  On  diluting  5  c.c.  of  glycerin  with  25  c.c.  of  water  and  adding 
hydrogen  sulphide  water,  no  change  should  appear.  (Indicating  none  present.) 

Calcium.  —  5  c.c.  of  glycerin  dissolved  in  25  c.c.  of  water  should  not  be 
affected  by  the  addition  of  ammonium  oxalate  solution.  (Indicating  less  than 
0.005  per  cent  Ca.) 

Sugars.  —  5  c.c.  of  glycerin  mixed  with  5  c.c.  of  water  and  5  drops  of  diluted 
hydrochloric  acid  are  warmed  a  few  minutes  on  a  boiling  water-bath,  then  3 
drops  of  solution  of  copper  sulphate  and  1  c.c.  of  solution  of  sodium  hydroxide 
are  added.  Upon  further  warming  no  pronounced  separation  of  cuprous  oxide 
should  occur.  (Indicating  less  than  0.04  per  cent  as  saccharose.) 

Readily  Carbonizable  Matter.  —  5  c.c.  of  glycerin  mixed  with  an  equal 
volume  of  concentrated  sulphuric  acid,  and  allowed  to  stand  one  hour,  should 
not  become  darker  than  yellow.  (Indicating  none  present.) 

Dextiose,  Ammonium  Compounds,  and  Organic  Bodies  Such  as  Occur  in 
Unpurified  Glycerin.  —  On  heating  on  a  water-bath  1  c.c.  of  glycerin  with  1 
c.c.  of  sodium  hydroxide  solution,  no  ammonia  should  be  evolved  (to  be  detected 
by  means  of  moistened  litmus  paper)  (indicating  less  than  0.003  per  cent 
NHs) ;  neither  should  a  color  develop,  nor  an  odor  resembling  that  of  glue.  (Indi- 
cating no  dextrose  and  organic  bodies  present.) 

Fatty  Acid  Esters.  —  50  c.c.  of  glycerin,  50  c.c.  of  water,  and  10  c.c.  of 
decinormal  solution  of  potassium  hydroxide  are  mixed  and  warmed  15  minutes 
on  a  boiling  water-bath.  After  cooling,  at  least  4  c.c.  of  decinormal  solution  of 
hydrochloric  acid  should  be  required  for  neutralization,  using  phenolphthalein  as 
indicator.  (Indicating  less  than  0.115  per  cent  as  ethyl  butyrate.) 

II 
GLYCERIN,  Sp.Gr.  1.23 

A  clear,   colorless,  almost  odorless  liquid  of  neutral  reaction. 
Soluble  in  all  proportions  in  water  and  in  alcohol.     Insoluble  in  ether 
and  in  chloroform.     Its  specific  gravity  is  1.225-1.235. 
TESTS   OF  PURITY 

The  tests  of  purity  are  to  be  made  in  the  manner  described  under  Glycerin, 
Sp.Gr.  1.250. 


84  CHEMICAL  REAGENTS 


GUAIACIN  ACCORDING  TO  SCHMITT  * 

Guaiacin  is  a  brownish,  amorphous  powder,  obtained  by  a  special 
method  from  guaiac  wood.  It  is  soluble  in  alcohol,  is  colored  blue 
by  oxidizers,  is  far  more  sensitive  than  guaiac  resin,  and  serves  as 
an  excellent  reagent  for  oxidases.  Guaiacin  is  used  in  the  form  of  a 
5  per  cent  alcoholic  solution,  which  keeps  well  in  completely  filled, 
dark-colored,  well-stoppered  bottles. 

HEMATEIN 

Ci8Hi2Ofl.    Mol.  Wt.  300.09 

Hematein  occurs  in  reddish-brown  plates,  presenting  a  yellowish- 
green  metallic  luster.  100  parts  of  water  at  20°  C.  dissolve  0.06 
part  of  hematein.  It  is  difficultly  soluble  in  ether  and  in  alcohol, 
and  is  insoluble  in  chloroform  and,  benzene;  but  it  is  soluble  in 
ammonia  water  with  brownish-violet  color,  and  in  dilute  sodium 
hydroxide  solution  with  a  bright-red  color. 

HEMATOXYLIN 

Ci6H1406+3H20.    Mol.  Wt.  356.16 

Colorless,  or  pale  yellow,  tetragonal  prisms,  melting  at  100°  to 
120°  C.  with  loss  of  water.  On  slowly  cooling  a  solution  saturated 
at  boiling  heat,  hematoxylin  crystallizes  at  times  in  the  form  of 
rhombic  crystals,  containing  one  molecule  of  water  of  crystallization. 
Hematoxylin  is  but  slightly  soluble  in  cold  water  and  in  ether, 
but  is  more  soluble  in  borax  solution  and  in  hot  water,  and  is  easily 
soluble  in  alcohol.  On  exposure  to  light  it  gradually  acquires  a 
red  color,  and  then  dissolves  to  form  pale  yellow  solutions.  In 
ammonia  water  hematoxylin  dissolves  and  yields  a  purple  solution. 
Hematoxylin  is  used  as  an  indicator  in  0.5  per  cent  alcoholic  solution. 

NOTE.  —  Regarding  the  use  of  hematoxylin  as  an  indicator  in  the  titration 
of  akaloids,  see  C.  Kippenberger,  Z.  anal.  Chem.,  39,  201  (1900);  abet.,  J.  Chem. 
Soc.,  78,  II,  637  (1900).  J.  Messner,  Z.  angew.  Chem.,  16,  444  (1903);  4  abst., 
J.  Chem.  Soc.,  84,  II,  519  (1903). 


*  Le  Bois  de  Gajac,  These  de  Nancy,  1875.  Report  on  the  Advancements 
of  Pharmaceutical  Chemistry  and  Therapeutics,  E.  Merck's  Annual  Report 
on  the  year  1902,  p.  75. 


HIDE  POWDER  85 


HIDE  POWDER 

White  or  yellowish-white,  woolly  powder,  prepared  from  the  best 
quality  of  hide  from  which  the  hair  has  been  removed  with  lime  and 
which  has  been  thoroughly  washed.  Hide  powder  should  have  but 
a  slight  odor  and  should  be  specially  free  from  odors  of  decomposition 
products.  It  is  used  for  tannin  determination. 

TEST  OF  PURITY 

Determination  of  the  Water-Soluble  Constituents.*  —  Introduce  7  gm.  of  the 
hide  powder  into  a  bell-filter,  as  described  by  Proctor  (see  Lunge,  Chem.-techn. 
Untersuch.-Meth.,  5  ed.,  3,  715  (1905);  Allen,  Com.  Org.  Anal.,  3  ed.,  Vol.  Ill, 
Ft.  I,  p.  83  (1900)).  Then  suspend  the  filter  in  a  beaker  of  about  150  to  200  c.c. 
capacity,  fix  the  siphon,  by  means  of  a  clamp,  so  that  the  bell-filter  almost  reaches 
the  bottom  of  the  beaker,  and  then  pour  into  the  beaker  a  small  quantity  of  water 
in  order  to  moisten  the  hide  powder  by  capillarity.  After  the  powder  has  become 
moist,  which  requires  about  an  hour,  the  beaker  is  filled,  and  suction  carefully 
applied  to  the  siphon  until  the  filtrate  begins  to  drop  slowly.  The  filtration  of 
90  to  100  c.c.  requires  about  one  and  a  half  to  two  hours.  The  30  c.c.  first  siphoned 
off  are  rejected;  the  next  50  c.c.  are  evaporated  to  dryness  on  the  water-bath. 
The  residue  from  the  evaporation  is  then  dried  to  constant  weight  in  an  air-bath 
at  100°  to  105°  C.  The  weight  of  this  residue,  conforming  to  the  requirements 
laid  down  by  the  International  Conference  of  Chemists  for  Leather  Industries, 
should  not  exceed  0.005  gm. 

HYDRAZINE  SULPHATE 

(NH2)2H2SO4.    Mol.  Wt.  130.14 

Colorless  crystals,  soluble  in  40  parts  of  cold,  and  in  8  parts  of 
boiling  water;  insoluble  in  alcohol.  The  aqueous  solution  (1  :  50) 
is  acid  to  litmus  paper. 

TESTS  OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  hydrazine  sulphate  in  50  c.c.  of  water 
should  not  be  more  than  slightly  opalescent  upon  the  addition  of  nitric  acid  and 
silver  nitrate.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  hydrazine  sulphate  in  50  c.c.  of 
water,  should  remain  unchanged  upon  addition  of  hydrogen  sulphide  water.  The 
further  addition  of  ammonia  water  and  ammonium  sulphide  solution  should 
produce  neither  a  green  or  brown  color  nor  a  precipitate.  (Indicating  none 
present.) 

Non-volatile  Matter.  —  Upon  volatilizing  1  gm.  of  hydrazine  sulphate  by 
heating,  no  weighable  residue  should  remain.  (Indicating  less  than  0.05  per  cent.) 


*  As  the  quantity  of  water-soluble  constituents  in  the  various  hide  powders 
varies  greatly,  it  is  always  necessary,  before  using  a  hide  powder  for  tannin 
determinations,  to  determine  the  quantity  of  soluble  constituents  by  a  blank 
test  according  to  the  method  described  here. 


86  CHEMICAL  REAGENTS 


Quantitative  Determination.  —  Titrate  1  gm.  of  hydrazine  sulphate,  dissolved 
in  100  c.c.  of  water,  with  normal  solution  of  potassium  hydroxide,  using  methyl 
orange  as  indicator. 

1  c.c.  of  normal  KOH  =  0.130138  gm.  9f  (NH2)2H2SO4,  log.  11440. 

Dissolve  1  gm.  of  hydrazine  sulphate  in  100  c.c.  of  water.  To  10  c.c.  of  this 
solution  add  1  gm.  sodium  bicarbonate  and  titrate  with  decinormal  solution  of 
iodine,  using  starch  solution  as  indicator. 

1  c.c.  of  decinormal  1  =  0.00325345  gm.  (NH2)2H2SO4,  log.  51234. 

HYDROGEN  PEROXIDE,  30  PER  CENT 

(Perhydrol) 
H2O2.    Mol.  Wt.  34.02 

A  colorless  liquid  of  specific  gravity  1.115  to  1.119,  containing 
about  30  per  cent  by  weight  of  hydrogen  peroxide.*  The  solution 
is  acid  to  litmus  paper,  f 

TESTS  OF  PURITY 

Free  Acids.  —  Dilute  10  c.c.  of  hydrogen  peroxide  with  100  c.c.  of  water  and 
then  decompose  it  with  small  pieces  of  platinum  black  or  manganese  dioxide. 
Allow  the  liquid  to  stand  with  repeated  shaking  until  the  oxygen  has  escaped, 
filter,  and  to  the  filtrate  add  solution  of  phenolphthalein  and  decinormal  solution 
potassium  hydroxide  until  a  pink  color  remains.  Not  more  than  one  drop  of 
the  solution  of  potassium  hydroxide  should  be  required.  (Indicating  none 
present.) 

Sulphuric  Acid.  —  Dilute  1  c.c.  of  the  hydrogen  peroxide  with  20  c.c.  of  water, 
add  1  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  add  barium  chloride  solution. 
No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indi- 
cating less  than  0.0075  per  cent  SO3.) 

Residue  on  Evaporation  (Sulphuric  and  Phosphoric  Acids,  etc.).  —  10  c.c.  of 
the  hydrogen  peroxide,  when  heated  on  the  water-bath,  should  completely  vola- 
tilize and  leave  no  weighable  residue.  (Indicating  less  than  0.0045  per  cent.) 

Oxalic  Acid.  —  The  solution  of  2  c.c.  of  hydrogen  peroxide  in  10  c.c.  of  water 
should  not  become  turbid  on  the  addition  of  calcium  chloride  solution.  Indicating 
less  than  0.035  per  cent  H2C2O4.) 

Hydrochloric  Acid.  —  The  solution  of  1  c.c.  of  hydrogen  peroxide  in  20  c.c. 
of  water  with  1  c  c.  of  nitric  acid  should  not  be  changed  on  the  addition  of  a  few 
drops  of  silver  nitrate  solution.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Hydrofluoric  Acid.  —  Evaporate  to  a  small  volume  10  c.c.  of  hydrogen  per- 
oxide mixed  with  0.1  gm.  of  magnesium  oxide,  transfer  the  concentrated  liquid 
to  a  watch  glass,  evaporate  to  dryness  on  the  latter,  pour  concentrated  sulphuric 
acid  over  the  residue,  and  allow  the  whole  to  stand  two  to  three  hours  in  a  warm 
place.  After  washing  off  the  glass,  no  etching  should  be  visible.  (Indicating  less 
than  0.005  per  cent  HF.) 

Phosphoric  Acid.  —  Concentrate  5  c.c.  of  hydrogen  peroxide  on  the  water- 
bath,  take  up  any  residue  with  3  c.c.  of  water,  and  add  1  c.c.  of  magnesia  mixture 


*  The  solution,  containing  30  per  cent,  by  weight,  of  hydrogen  peroxide, 
is  also  designated  as  "  100- volumes  hydrogen  peroxide,"  because  this  solution 
is  capable  of  yielding  100  times  its  volume  of  free  oxygen. 

f  The  acid  reaction  is  entirely  due  to  the  high  content  of  hydrogen  peroxide. 


HYDROGEN  SULPHIDE  WATER  87 


and  3  c.c.  of  ammonia  water.  No  precipitation  should  take  place  on  standing 
fifteen  hours.  (Indicating  less  than  0.0006  per  cent  P2Os.) 

Quantitative  Determination.  —  Weigh  off  1  gm.  of  hydrogen  peroxide  in  a 
graduated  flask  of  100  c.c.  capacity,  and  fill  with  water  to  the  mark.  Dilute  20 
c.c.  of  this  liquid  with  50  c.c.  of  water,  add  20  c.c.  of  16  per  cent  sulphuric  acid, 
and  titrate  with  decinormal  potassium  permanganate.  At  least  35  c.c.  should 
be  required  to  produce  the  end-point. 

1  c.c.  of  decinormal  KMnO4  =  0.0017008  gm.  of  H2O2,  log.  23065. 


HYDROGEN   SULPHIDE  WATER 

A  clear,  colorless  liquid,  having  a  strong  odor  of  hydrogen  sul- 
phide gas,  and  affording  a  voluminous  precipitate  of  sulphur  on  the 
addition  of  ferric  chloride  solution.  Hydrogen  sulphide  water  has 
an  acid  reaction  to  litmus  paper. 

TEST   OF  PURITY 

Iron.  —  Hydrogen  sulphide  water  should  not  be  changed  upon  the  addition  of 
ammonia  water.  (Indicating  none  present.) 


HYDROXYLAMINE  HYDROCHLORIDE 

NH2OH  HC1.    Mol.  Wt.  69.50 

Colorless  crystals,  soluble  in  1.5  parts  of  water  and  in  15  parts 
of  alcohol,  and  also  in  glycerin.  The  aqueous  solution  is  acid  to 

litmus  paper. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  1  gm.  of  hydroxylamine  hydrochloride,  heated  on 
platinum  foil,  should  volatilize  and  leave  no  weighable  residue.  (Indicating  less 
than  0.05  per  cent.) 

Ammonium  Chloride.  —  The  1  :  20  alcoholic  solution  should  afford  no  pre- 
cipitate on  adding  platinic  chloride  solution.  (Indicating  less  than  0.3  per  cent.) 

Sulphuric  Acid.  —  On  adding  barium  chloride  solution  to  20  c.c.  of  a  1  :  10 
aqueous  solution  of  hydroxylamine  hydrochloride,  no  precipitate  of  barium  sul- 
phate should  form  within  fifteen  hours.  (Indicating  less  than  0.0005  per  cent  SO?.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  hydroxylamine  hydrochloride  in 
20  c.c.  of  water  should  show  scarcely  any  change  upon  the  addition  of  hydrogen 
sulphide  water.  (Indicating  at  most  a  trace.) 

Arsenic.  —  Upon  thoroughly  mixing  1  gm.  of  hydroxylamine  hydrochloride 
and  3  c.c.  of  solution  of  tin  chloride  no  dark  color  should  appear  within  one 
hour.  (Indicating  less  than  0.0015  per  cent  As.) 

Quantitative  Determination. —  Dissolve  1  gm.  of  hydroxylamine  hydrochloride 
in  water  and  dilute  to  100  c.c.  After  boiling  10  c.c.  of  this  solution  five  minutes 
with  20  c.c.  of  a  solution  of  ferric  ammonium  sulphate  (saturated  in  the  cold) 
and  10  c.c.  of  diluted  sulphuric  acid,  dilute  with  25  c.c.  of  boiled  water  and  titrate 
with  decinormal  solution  of  potassium  permanganate. 

1  c.c.  of  decinormal  KMnO4  =  0.003475  gm.  of  NH2OH  HC1,  log.  54095. 


88  CHEMICAL  REAGENTS 

INDIGO 

I 

SYNTHETIC  INDIGO 

A  fine,  dark-blue  powder,  containing  at  least  95  per  cent  of 

indigo  blue. 

TESTS   OF  PURITY 

Ash.  —  1  gm.  of  indigo  upon  ignition  should  leave  a  residue  not  exceeding 
0.01  gm.  in  weight.  (Indicating  not  more  than  1  per  cent.) 

Moisture.  —  On  drying  1  gm.  of  indigo  at  100°  C.  to  constant  weight,  the  loss 
of  weight  should  not  exceed  0.01  gm.  (Indicating  not  more  than  1  per  cent.) 

Quantitative  Determination  of  Indigo  Blue  (Indigotin).  —  Warm  on  a  water- 
bath  0.5  gm.  of  finely  powdered  indigo  in  a  beaker  with  10  gm.  concentrated 
sulphuric  acid,  frequently  stirring  until  dissolved,  and  dilute  to  1  liter.  To 
50  c.c.  of  the  solution  add  600  c.c.  of  water,  and  titrate  with  decinormal  solution  of 
potassium  permanganate.  The  end-point  is  the  change  from  green  to  light 
yellow,  not  the  incipient  red  color. 

1  c.c.  of  decinormal  KMn04  =  0.007493  gm.  of  indigotin,*  log.  87466. 

II 
VEGETABLE  INDIGO 

Dark-blue,  light  pieces,  which,  on  being  rubbed  with  a  horn 
spoon,  or  other  hard  substance,  exhibit  a  coppery  luster.  Vegetable 
indigo  should  contain  at  least  60  per  cent  of  indigo  blue. 

TESTS  OF  PURITY 

Ash.  —  1  gm.  of  indigo  should  not  leave  more  than  0.12  gm.  of  ash.  (Indi- 
cating not  more  than  12  per  cent.) 

Moisture.  —  On  drying  1  gm.  of  indigo  to  constant  weight  at  100°  C.,  the  loss 
in  weight  should  not  exceed  0.06  gm.  (Indicating  not  more  than  6  per  cent.) 

Quantitative  Determination  of  Indigo  Blue  (Indigotin).  —  Warm  on  the  water- 
bath  one  or  two  hours,  1  gm.  of  finely  powdered  indigo  with  20  gm.  of  concentrated 
sulphuric  acid,  stirring  thoroughly.  Dilute  to  1  liter,  filter,  and  to  50  c.c.  of  the 
filtrate  add  50  c.c.  of  water  and  32  gm.  of  sodium  chloride.  After  standing 
two  hours,  filter,  wash  the  precipitate  with  saturated  solution  of  sodium  chloride, 
and,  after  dissolving  the  precipitate  in  hot  water,  add  500  c.c.  of  water  containing 
1  c.c.  of  sulphuric  acid,  and  titrate  with  decinormal  solution  of  potassium  per- 
manganate. The  end-point  is  the  change  from  green  to  light  yellow,  not  the 
incipient  red  color. 

1  c.c.  of  decinormal  KMn04  =  0.007493  gm.  indigotin,*  log.  87466. 

*  O.  Miller  &  J.  Smirnoff,  Ber.,  41,  1366  (1908);  abst.,  J.  Chem.  Soc.,  94,  I, 
468  (1908). 


INDIGO  SOLUTIONS  89 

INDIGO    SOLUTIONS 

I 
INDIGO   SOLUTION,   1:40 

4  gm.  of  synthetic  indigo  are  heated  upon  the  water-bath  with 
28  gm.  of  Acid  Sulphuric,  Fuming  (8  to  10  per  cent  free  SOa),  with 
frequent  stirring  until  solution  results.  This  solution  after  cooling 
is  poured  into  128  c.c.  of  water. 

II 
INDIGO   SOLUTION,   1  :  1000 

This  solution  is  prepared  by  diluting  4  c.c.  of  Indigo  Solution, 
1  :  40,  with  96  c.c.  of  water. 

IODEOSIN 

(Tetraiodofluore  scein) 
C20H8I4Of.     Mol.  Wt.  835.74 

A  scarlet-red  powder,  yielding  with  alcohol  a  deep-red,  and  with 
ether  a  yellowish-red,  solution.  lodeosin  is  insoluble  in  water  con- 
taining a  trace  of  hydrochloric  acid.  The  solution  used  as  an  indicator 
is  prepared  by  dissolving  1  gm.  of  iodeosin  in  100  c.c.  of  boiling 
alcohol  (about  85  per  cent  by  weight),  diluting  to  500  c.c.  with 
alcohol,  and  filtering  after  standing  twenty-four  hours. 

TEST  OF  SENSITIVENESS 

Introduce  100  c.c.  of  water,  containing  5  drops  of  the  above  iodeosin  solution, 
into  a  colorless,  glass-stoppered  flask,  and  then  overlay  it  with  30  c.c.  of  ether. 
Then  run  in  by  drops,  from  a  burette,  centinormal  hydrochloric  acid  solution, 
vigorously  shaking  after  the  addition  of  each  drop,  until  the  aqueous  layer  just 
becomes  colorless.  Now  add  5  drops  more  of  the  iodeosin  solution.  After 
shaking  again,  the  aqueous  layer  must  not  acquire  a  pink  color;  or,  should  it 
do  so,  the  color  must  disappear  on  the  addition  of  1  drop  of  centinormal  hydro- 
chloric acid  solution. 

NOTE.  —  Regarding  the  use  of  iodeosin  for  the  estimation  of  alkaloids,  see 
C.  Kippenberger,  Z.  anal.  Chem.,  39,  205  (1900);  abst.,  J.  Chem.  Soc.,  78,  II,  637 
(1900).  Merck's  Berichte,  9,  32  (1900);  Merck's  Annual  Report,  13,  37  (for 
the  year  1900). 


90  CHEMICAL  REAGENTS 

IODINE 

(Iodine  Resublimed) 
I.    Atomic  Wt.  126.92 

Blackish-gray,  dry,  rhombic  plates  or  scales,  with  a  metallic 
luster,  easily  soluble  in  alcohol,  ether,  and  chloroform.  Iodine  dis- 
solves in  about  4500  parts  of  water,  and  is  very  freely  soluble  in 
an  aqueous  solution  of  potassium  iodide.  The  preparation  con- 
tains 100  per  cent  of  I. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  On  cautiously  heating  1  gm.  of  iodine  in  a  porcelain 
dish,  no  weighable  residue  should  remain.  (Indicating  less  than  0.05  per  cent.) 

Cyanogen,  Chlorine,  and  Bromine.  —  Shake  0.5  gm.  of  powdered  iodine  with 
20  c.c.  of  water,  and  filter.  To  10  c.c.  of  the  filtrate,  add,  drop  by  drop,  sul- 
phurous acid  until  decolorized,  then  add  a  granule  of  ferrous  sulphate,  1  drop  of 
ferric  chloride  solution  and  2  c.c.  of  sodium  hydroxide  solution.  Warm  to  about 
60°  C.,  and  add  10  c.c.  of  hydrochloric  acid.  The  liquid  should  not  acquire  a 
blue  color.  (Indicating  less  than  0.05  per  cent  CN.)  To  the  other  10  c.c.  of  the 
filtrate  add  1  c.c.  of  ammonia  water  and  5  drops  of  silver  nitrate  solution,  and 
again  filter.  On  adding  to  the  filtrate  2  c.c.  of  nitric  acid  no  precipitate,  and 
not  more  than  an  opalescent  turbidity,  should  develop.*  (Indicating  less  than 
0.12  per  cent  Cl  and  Br  as  Cl.) 

Quantitative  Determination.  —  Dissolve  0.2  gm.  of  iodine,  and  1  gm.  of 
potassium  iodide  in  1  c.c.  of  water,  add  50  c.c.  of  water,  and  titrate  with  deci- 
normal  solution  of  sodium  thiosulphate.  f 

1  c.c.  of  decinormal  Na2S2O3  =  0.012692  gm.  of  I,  log.  10352. 

IODINE  WATER 

A  saturated  aqueous  solution,  containing  about  0.2  gm.  of  iodine 

in  1000  c.c. 

TEST  OF  STRENGTH 

Titrate  100  c.c.  of  iodine  water  with  decinormal  sodium  thiosulphate  solution. 
1  c.c.  of  decinormal  Na2S2O3  =  0.012692  gm.  of  I,  log.  10352 

IRON 

Fe.    Atomic  Wt.  55.84 

Metallic  iron  is  used  in  the  analytical  laboratory  in  the  form  of 
thin,  polished  wire  (piano  wire),  or  gray  powder  obtained  by  reduc- 


*  The  filtrate  contains  traces  of  dissolved  silver  iodide;  hence,  on  acidulating 
with  nitric  acid  some  opalescence  always  occurs. 

f  The  titer  of  the  decinormal  sodium  thiosulphate  solution  should  be  controlled 
by  means  of  potassium  biniodate. 


IRON  WIRE  91 

tion  with  hydrogen  (iron  by  hydrogen),  and  also  in  the  form  of  the 
ordinary  gray,  lustrous  powdered  iron. 


IRON  WIRE 

(Piano  Wire) 

Iron  wire  serves  chiefly  for  the  standardization  of  potassium  per- 
manganate solutions.  It  was  formerly  believed,  without  further 
consideration,  that  the  wire  contained  99.6  to  99.8  per  cent  of  pure, 
active  iron.  Treadwell,  however,  has  shown  that  the  various  kinds 
of  wire  exhibit  a  decidedly  variable  value  towards  potassium  per- 
manganate solution,  and  that  several  exhibit  a  value  corresponding 
to  over  100  per  cent  of  Fe,  which  statement  is  fully  confirmed  by 
Lunge.  The  explanation  of  this  lies  in  the  presence  of  carbon  in 
the  wire,  principally  as  carbide  of  iron,  which,  upon  dissolving  in 
acid,  becomes  converted  into  hydrocarbons,  exerting  a  marked 
reducing  action  on  the  permanganate. 

Notwithstanding  this,  iron  wire  is  a  convenient,  unalterable, 
and  also  perfectly  reliable  substance  for  standardizing  permanganate 
solutions,  if  we  have  once  ascertained  its  effective  value  compared 
with  potassium  permanganate  solution  the  titer  of  which  has  been 
accurately  determined  by  means  of  some  other  standard. 

For  a  satisfactory  means  of  fixing  the  titer  of  permanganate 
solution,  sodium  oxalate  may  be  recommended  (see  Sodium  Oxalate, 
according  toSorensen).  Or*  starting  with  sodium  bicarbonate,  by 
drying  the  latter  at  about  300°  C.,  thus  obtaining  sodium  carbonate, 
preparing  a  standard  solution  of  this,  from  this  preparing  a  solution 
of  fifth-normal  hydrochloric  acid,  from  this  a  solution  of  fifth-normal 
potassium  hydroxide,  from  this  a  solution  of  oxalic  acid,  and  finally 
a  solution  of  the  permanganate. f  Where  a  gas  volumeter  is  at 
hand,  the  titer  may  also  be  ascertained  with  hydrogen  peroxide, 


*G.  Lunge,  Z.  angew.  Chem.,  17,  267  (1904);  dbst.,  J.  Chem.  Soc.,  86,11, 
289  (1904). 

f  For  titrations  in  hydrochloric  acid  solutions,  use  a  titer  obtained  in  the 
same  way.  The  oxalic  acid  titer  is,  according  to  Reinhardt,  not  suitable  for 
the  iron  titration. 


92  CHEMICAL  REAGENTS 

according  to  the  nitrometer  method.  (G.  Lunge,  Chem.-tech. 
Untersuch.-Meth.,  5  ed.,  1,  127,  (1904).  J.  Chem.  Soc.,  58,  1468 
(1890). 

II 
IRON  BY  HYDROGEN 

(Reduced  Iron) 
A  gray,  lusterless,  fine  powder,  containing  at  least  90  per  cent  of  Fe. 

TESTS   OF  PURITY 

Solubility  in  Sulphuric  Acid.  — 10  gm.  of  reduced  iron  are  dissolved  in  a 
mixture  of  20  c.c.  of  sulphuric  acid  (sp.gr.  1.84)  and  200  c.c.  of  water.  The 
insoluble  residue  should  be  filtered  off,  and  when  dried  at  100°  C.,  its  weight 
should  not  exceed  0.05  gm.  (Indicating  not  more  than  0.5  per  cent  insoluble 
matter.) 

Sulphides.  —  Pour  a  mixture  of  10  c.c.  of  hydrochloric  acid  and  10  c.c.  of 
water  over  1  gm.  of  reduced  iron  in  a  test-tube.  Filter  paper  moistened  with 
solution  of  lead  acetate  should  not  be  darkened  in  color  on  exposure  for  one 
minute  to  the  liberated  hydrogen.  (Indicating  less  than  0.007  per  cent  S.) 

Sodium  Carbonate.  —  On  shaking  5  gm.  of  reduced  iron  with  50  c.c.  of  water 
and  filtering,  the  filtrate  should  not  turn  red  litmus  paper  blue;  and  on  evapora- 
tion it  should  leave  not  more  than  0.003  gm.  of  residue.  (Indicating  not  more 
than  0.06  per  cent.) 

Nitrogen.  —  Dissolve  20  gm.  of  reduced  iron  in  a  mixture  of  20  c.c.  of  con- 
centrated sulphuric  acid  (sp.gr.  1.84)  and  200  c.c.  of  water,  with  the  aid  of  heat. 
Allow  to  cool,  and  when  cold  add  100  c.c.  of  nitrogen-free  sodium  hydroxide 
solution  I,  and  distil  off  about  75  c.c.,  collecting  the  distillate  in  a  receiver  containing 
about  10  c.c.  of  water  and  2  to  3  c.c.  of  fifth-normal  hydrochloric  acid.  Titrate 
the  distillate  with  fifth-normal  potassium  hydroxide  solution,  using  methyl  orange 
as  indicator.  The  ammonia  from  the  iron  should  not  neutralize  more  than 
0.2  c.c.  of  the  acid.  (Indicating  not  more  than  0.0028  per  cent  N.) 

Arsenic.  —  Pour  10  c.c.  of  hydrochloric  acid  over  a  mixture  of  1  gm.  of 
reduced  iron  and  1  gm.  of  potassium  chlorate,  and  when  the  reaction  has  subsided, 
heat  until  all  free  chlorine  had  been  expelled,  and  filter.  On  now  adding  15  c.c. 
of  stannous  chloride  solution  to  5  c.c.  of  the  filtrate,  a  dark  coloration  should 
not  develop  within  one  hour.  (Indicating  less  than  0.0015  per  cent  As.) 

Quantitative  Determination.  —  Introduce  into  a  graduated  flask  of  100  c.c. 
capacity  1  gm.  of  reduced  iron,  10  gm.  of  finely  powdered  mercuric  chloride, 
and  50  c.c.  of  boiling  water.  Place  the  flask  on  wire  gauze,  heat  over  a  small 
flame,  boil  about  five  minutes  with  frequent  shaking,  then  immediately  fill  the 
flask  to  the  mark  with  cold,  boiled  water.  Cool  the  mixture  to  15°  C.,  add  water 
to  the  mark,  shake  thoroughly,  and,  tightly  stoppering  the  flask,  set  it  aside  to 
deposit.  Now  filter,  and  to  10  c.c.  of  the  filtrate  add  immediately  10  c.c.  of  16 
per  cent  sulphuric  acid,  and  titrate  with  decinormal  potassium  permanganate 
until  a  faint  red  color  persists.  At  least  16.2  c.c.  of  the  permanganate  solution 
should  be  required. 

After  the  pink  color  has  been  destroyed  by  the  addition  of  solution  of  tartaric 
acid,  dissolve  in  the  liquid  2  gm.  of  potassium  iodide,  allow  to  stand  two  hours 


IRON  POWDER  93 


in  the  stoppered  flask  at  room  temperature,  and  titrate  with  decinormal  sodium 
thiosulphate  solution,  using  starch  solution  as  the  indicator. 

1  c.c.  of  decinormal  KMnO4  or  1  c.c.  of  decinormal  Na2S2O3  =  0.005584  gm. 
of  Fe,  log.  74695. 

Ill 
IRON  POWDER 

A  fine,  heavy,  gray  powder  with  metallic  luster,  and  containing 
at  least  97.7  per  cent  of  Fe. 

TESTS  OF  PURITY 

Solubility  in  Sulphuric  Acid.  — 10  gm.  of  powdered  iron  are  dissolved  in  a 
mixture  of  20  c.c.  of  concentrated  sulphuric  acid  (sp.gr.  1.84)  and  200  c.c.  of  water. 
The  insoluble  residue  should  be  filtered  off  through  a  filter  previously  dried  at 
100°  C.  and  weighed;  the  filter  and  residue  are  then  washed,  and  dried  at  100° 
C.  and  weighed.  The  weight  of  the  residue  should  not  exceed  0.01  gm.  (Indi- 
cating not  more  than  0.1  per  cent  insoluble  matter.) 

Nitrogen  and  Arsenic.  —  These  tests  are  carried  out  as  detailed  under  Iron 
by  Hydrogen. 

Foreign  Heavy  Metals.  —  Dissolve  1  gm.  of  powdered  iron  in  10  c.c.  of  hydro- 
chloric acid  mixed  with  5  c.c.  of  nitric  acid,  and  heat  the  solution  until  it  has  a 
brown  color.  Dilute  the  solution  with  35  c.c.  of  water,  add  30  c.c.  of  ammonia 
water,  and  filter.  The  filtrate  should  not  have  a  blue  color;  nor  should  it  show 
any  change  on  the  addition  of  hydrogen  sulphide  water.  (Indicating  none 
present.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  powdered  iron  in  about 
50  c.c.  of  dilute  sulphuric  acid,  and  dilute  the  solution  to  100  c.c.  To  10  c.c.  of 
this  solution  add  decinormal  potassium  permanganate  solution  until  the  liquid 
has  a  slight  red  color,  and,  after  destroying  the  red  color  by  the  addition  of 
tartaric  acid  solution,  add  2  gm.  of  potassium  iodide.  Allow  the  mixture  to  stand 
two  hours  in  a  closed  flask  at  room  temperature,  and  then  titrate  with  decinormal 
solution  of  sodium  thiosulphate  with  starch  solution  as  indicator.  At  least  17.5 
c.c.  should  be  required  to  combine  with  the  liberated  iodine. 

1  c.c.  of  decinormal  Na2S2O3  =  0.005584  gm.  of  Fe,  log.  74695. 

IRON   CHLORIDE,   FERRIC 

FeCl3+6H2O.    Mol.  Wt.  270.31 

Yellow,  crystalline  masses,  very  deliquescent  in  air.  Ferric 
chloride  is  easily  soluble  in  water,  alcohol,  and  a  mixture  of  alcohol 
and  ether.  The  solutions  are  acid  to  litmus  paper. 

TESTS  OF  PURITY 

Basic  Salt  and  Other  Matter  Difficultly  Soluble  in  Water.  —  10  gm.  of  ferric 
chloride  should  completely  dissolve  in  10  c.c.  of  water,  and  yield  a  perfectly  clear 
solution.  (Indicating  none  present.) 

Hydrochloric  Acid  and  Chlorine.  — On  boiling  10  c.c.  of  a  solution  (1  :  1)  of 
ferric  chloride  for  2  or  3  minutes  in  a  test-tube  capped  with  blue  litmus  paper, 
the  paper  should  not  be  reddened.  (Indicating  less  than  0.35  per  cent  HC1.)  In 


94  CHEMICAL  REAGENTS 


a  similar  test  employing  zinc  iodide-starch  paper,  the  latter  should  not  be  turned 
blue.  (Indicating  less  than  0.001  per  cent  Cl.) 

Arsenic.  —  A  mixture  of  1  c.c.  of  ferric  chloride  solution  (1  :  1)  and  3  c.c. 
of  stannous  chloride  solution  should  not  acquire  a  darker  color  within  one  hour. 
(Indicating  less  than  0.0011  per  cent  As.) 

Ferrous  Salt.  —  Add  1  c.c.  of  hydrochloric  acid  and  a  few  drops  of  potassium 
ferricyanide  solution  to  the  1  :  20  aqueous  solution  of  ferric  chloride;  no  blue 
color  should  develop.  (Indicating  less  than  0.0025  per  cent  Fe".) 

Zinc,  Copper,  Nitric  Acid,  etc.  (Alkali  Salts,  Calcium).  —  Dilute  20  c.c.  of 
ferric  chloride  solution  (1:1)  with  100  c.c.  of  water,  add  30  c.c.  of  ammonia 
water,  filter,  and  bring  the  filtrate  to  a  volume  of  75  c.c.  by  washing.  On  evapor- 
ating 50  c.c.  of  the  filtrate,  which  must  be  colorless,  and  igniting  the  residue,  the 
weight  of  the  latter  should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.01 17 
percent  alkali  salts,  calcium,  etc.)  On  mixing  2  c.c.  of  the  filtrate  with  2  c.c.  of 
concentrated  sulphuric  acid,  and  overlaying  this  mixture  with  1  c.c.  of  ferrous 
sulphate  solution,  no  brown  zone  should  form  at  the  contact-surfaces  of  the  two 
liquids.  (Indicating  less  than  0.025  per  cent  N2O6.)  The  remainder  of  the  fil- 
trate acidulated  with  acetic  acid  and  treated  with  potassium  f errocyanide  solution 
should  show  neither  a  white  nor  a  brownish-red  precipitate  upon  standing  two 
hours.  (Indicating  less  than  0.0015  per  cent  Zn  and  less  than  0.005  per  cent  Cu.) 

Sulphates.  —  Dissolve  10  gm.  of  ferric  chloride  in  100  c.c.  of  water,  add  25 
c.c.  of  ammonia  water,  filter,  acidulate  the  filtrate  with  acetic  acid,  and  add  barium 
chloride  solution.  No  precipitate  of  barium  sulphate  should  form  on  standing 
fifteen  hours.  (Indicating  less  than  0.0025  per  cent  SO3.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ferric  chloride  in  100  c.c. 
of  water,  add  2  gm.  of  potassium  iodide  and  5  c.c.  of  hydrochloric  acid.  After 
allowing  the  mixture  to  stand  in  a  well-closed  flask  for  about  two  hours,  titrate 
the  free  iodine  with  decinormal  solution  of  sodium  thiosulphate. 

1  c.c.  of  decinormal  Na2S2O3  =  0.016222  gm.  FeCl3,  log.  21010,  or  0.0270315 
gm.  FeCl3+6H2O,  log.  43187. 

IRON  CHLORIDE,  FERRIC,   SOLUTION 

A  clear,  deep  yellowish-brown  liquid,  of  specific  gravity  1.280 
to  1.282.  100  parts  contain  10  parts  of  Fe,  =29  parts  of  FeCls. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Iron  Chloride,  Ferric.  But,  for 
each  gram  of  the  crystallized  ferric  chloride,  2  gm.  of  the  solution  of  ferric  chloride 
are  to  be  taken. 

IRON   CHLORIDE,  FERROUS 

FeCl,+4H2O.     Mol.  Wt.  198.82 

A  pale-green  hygroscopic  powder,  soluble  in  an  equal  weight  of 
water  acidulated  with  a  few  drops  of  hydrochloric  acid.  Ferrous 
chloride  is  also  soluble  in  alcohol. 

TESTS   OF  PURITY 

Oxychloride.  —  The  solution  of  1  gm.  of  ferrous  chloride  in  1  c.c.  of  water 
and  2  to  3  drops  of  hydrochloric  acid  should  be  pale  green  or  green  in  color,  and 


IRON  OXIDE  95 


should  not  have  any  yellowish-green  tint.  On  adding  hydrogen  sulphide  water, 
the  solution  should  show  only  a  very  slight  turbidity,  due  to  the  separation  of 
sulphur.  (Indicating  at  most  a  small  amount.*) 

Sulphates,  Copper,  Zinc,  and  Salts  of  the  Alkalies.  —  Heat  a  solution  of  5 
gm.  of  ferrous  chloride  in  10  c.c.  of  water  and  5  c.c.  of  nitric  acid  (sp.gr.  1.3) 
until  brown  in  color,  dilute  to  120  c.c.,  add  30  c.c.  of  ammonia  water,  filter, 
and  bring  the  nitrate  to  a  volume  of  75  c.c.  by  washing.  The  filtrate  should  be 
colorless.  Evaporate  50  c.c.  of  the  filtrate  and  ignite  the  residue.  The  weight 
of  the  latter  should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.03 
per  cent  alkali  salts.)  Acidulate  20  c.c.  of  the  filtrate  with  acetic  acid  and  add 
barium  chloride  solution.  No  cloudiness'  should  appear  within  five  minutes. 
(Indicating  less  than  0.0075  per  cent  SO3.)  The  remainder  of  the  filtrate 
acidified  with  acetic  acid  should  show  neither  a  white  nor  a  brownish-red  pre- 
cipitate upon  addition  of -potassium  ferrocyanide  solution,  followed  by  two 
hours'  standing.  (Indicating  less  than  0.0075  per  cent  Zn  and  less  than  0.03 
per  cent  Cu.) 

Arsenic.  —  The  solution  of  1  gm.  of  ferrous  chloride  in  1  c.c.  of  water  acidu- 
lated with  a  few  drops  of  hydrochloric  acid,  should  not  acquire  a  darker  color  on 
adding  3  c.c.  of  stannous  chloride  solution  and  standing  one  hour.  (Indicating 
less  than  0.0015  per  cent  As.) 

IRON   OXIDE 

Brandt's  Ferric  Oxide  f 
Fe2O3.    Mol.  Wt.  159.68 

A  reddish-brown  powder  soluble  in  concentrated  hydrochloric 
acid.  The  preparation  is  used  as  a  starting  material  for  making 
standardized  solutions  of  potassium  permanganate,  especially  for  the 
determination  of  iron  in  hydrochloric  acid  solution.  It  should  be 
dried  at  120°  C.  immediately  before  using. 

TESTS  OF  PURITY 

Water  and  Volatile  Substances.  —  The  iron  oxide  is  dried  to  constant  weight 
at  120°  C.  3  gm.  of  this  dry  material  should  not  lose  more  than  0.003  gm.  in 
weight  upon  ignition.  (Indicating  not  more  than  0.1  per  cent.)  Avoid  the 
contact  of  the  reducing  flame  with  the  platinum  crucible. 

Substances  Soluble  in  Water.  —  Heat  to  boiling  100  c.c.  of  water  with  5  gm. 
of  the  iron  oxide  and  then  filter.  50  c.c.  of  the  filtrate,  which  must  be  perfectly 
clear,  should  leave  no  weighable  residue  upon  evaporation  followed  by  ignition. 
(Indicating  less  than  0.01  per  cent.) 

Chlorides.  —  Fuse  in  a  platinum  crucible  a  mixture  of  1  gm.  of  the  iron  oxide 
and  3  gm.  of  anhydrous  sodium  carbonate.  After  cooling,  leach  the  melt  with 
50  c.c.  of  hot  water,  filter  the  solution,  acidulate  the  filtrate  with  20  c.c.  of  nitric 
acid,  and  add  silver  nitrate  solution.  At  most  only  an  opalescence  may  appear. 
(Indicating  less  than  0.005  per  cent  Cl.) 


*  Small  amounts  of  iron  oxychloride  are  always  present  in  ferrous  chloride. 
t  L.  Brandt,  Chem.,  Ztg.,  32,  812,  830,  840,  851  (1908V,  &3t.,  J.  Chem.  Soc., 
94,  II,  899  (1908). 


96  CHEMICAL  REAGENTS 


Nitrates.  —  Heat  to  boiling  a  mixture  of  5  c.c.  of  30  per  cent  acetic  acid  and 
10  c.c.  of  water  with  1  gm.  of  the  iron  oxide,  filter,  and  to  the  filtrate  add  1  drop 
of  1  :  1000  indigo  solution  and  10  c.c.  of  concentrated  sulphuric  acid.  The  blue 
color  of  the  fluid  should  not  disappear  on  shaking.  (Indicating  less  than  0.0032 
per  cent  N2Os.) 

Sulphates.  —  A  mixture  of  1  gm.  of  the  iron  oxide  with  a  solution  of  4  gm. 
crystallized  sodium  carbonate  in  20  c.c.  of  water  is  heated  one  hour  on  a  boiling 
water-bath  with  repeated  shaking,  and  then  filtered.  The  filtrate,  after  the 
addition  of  10  c.c.  of  hydrochloric  acid,  is  heated  to  boiling  and  mixed  with  barium 
chloride  solution.  After  standing  two  hours  there  should  be  no  separation  of 
barium  sulphate.  (Indicating  less  than  0.035  per  cent  SO3.) 

Silicates.  —  Fuse  in  a  platinum  crucible  a  mixture  of  3  gm.  of  the  iron  oxide 
and  15  gm.  of  anhydrous  sodium  carbonate,  leach  the  cooled  melt  with  hot  water, 
and  filter  the  solution.  Acidulate  the  filtrate  with  hydrochloric  acid,  evaporate 
it  in  a  platinum  dish,  dry  the  residue  one-half  hour  at  about  120°  C.,  and  then 
dissolve  it  in  10  c.c.  of  hydrochloric  acid,  and  50  c.c.  of  water.  Filter  the  solution, 
wash  with  water,  and  incinerate  the  filter.  The  weight  of  the  ash  should  be 
not  more  than  0.001  gm.  (Indicating  not  more  than  0.033  per  cent  SiO2.) 

Ferrous  Oxide.  —  Dissolve  1  gm.  of  the  iron  oxide  by  warming  on  the  water- 
bath  with  10  c.c.  of  fuming  hydrochloric  acid,  and  dilute  the  solution  with  40 
c.c.  of  water.  On  mixing  this  solution  with  potassium  ferricyanide  solution, 
neither  a  green  nor  a  blue  color  should  appear.  (Indicating  less  than  0.003 
per  cent.) 

Substances  Insoluble  in  Hydrochloric  Acid,  Foreign  Heavy  Metals,  Lime  and 
Magnesia. — Dissolve  10  gm.  of  the  iron  oxide  in  70  c.c.  of  fuming  hydrochloric 
acid  by  warming  on  the  water-bath.  The  solution,  diluted  with  200  c.c.  of 
water,  should  be  perfectly  clear  and  should  contain  no,  or  only  an  exceedingly 
slight,  insoluble  residue.  '  In  the  latter  case  filter  the  solution,  wash  the  residue, 
first  with  diluted  hydrochloric  acid  and  then  with  water,  ignite  and  weigh.  The 
weight  of  the  residue,  insoluble  in  hydrochloric  acid,  should  not  exceed  0.001  gm. 
(Indicating  not  over  0.01  per  cent  insoluble  substances.) 

Pass  hydrogen  sulphide  gas  into  the  filtrate  until  the  ferric  chloride  is  fully 
reduced;  the  separated  sulphur  should  not  be  dark-colored.  Filter  the  fluid. 
Warm  the  sulphur  in  a  porcelain  dish  on  the  water-bath  with  fuming  hydrochloric 
acid  and  filter  the  solution  after  diluting  it  with  water.  Ignite  the  residue  together 
with  the  filter  in  the  porcelain  dish,  dissolve  the  ash  in  hydrochloric  acid,  and 
combine  this  solution  with  the  hydrochloric  acid  extract.  On  passing  into  this 
solution  hydrogen  sulphide  gas,  neither  a  coloration  nor  the  separation  of  a  pre- 
cipitate should  occur.  (Indicating  no  foreign  heavy  metals  present.) 

Boil  the  filtrate  obtained  after  precipitation  with  hydrogen  sulphide  until 
the  hydrogen  sulphide  is  expelled,  then  oxidize  with  nitric  acid  and  add  an  excess 
of  ammonia  water.  Warm  the  solution  until  the  odor  of  ammonia  has  almost 
disappeared,  filter,  and  wash  the  precipitate  with  hot  water.  Dissolve  a  part 
of  the  precipitate  of  ferric  hydroxide,  about  half,  in  hydrochloric  acid,  and  after 
diluting  with  water,  precipitate  hot  with  sodium  hydroxide  solution  (30  gm.  of 
sodium  hydroxide,  from  sodium,  in  70  c.c.  of  water)  in  a  platinum  dish  and  filter. 
Acidulate  the  filtrate  with  hydrochloric  acid,  add  ammonia  water  to  alkaline 
reaction,  and  warm  until  the  odor  of  ammonia  has  disappeared.  No,  or  only  an 
exceedingly  slight,  flocculent  precipitate  should  be  perceptible.  In  the  latter 
case,  filter,  wash,  and  ignite  the  precipitate.  The  weight  of  the  residue  should 
not  exceed  0.001  gm.  (Indicating  not  more  than  about  0.02  per  cent  A12O3.) 

Fuse  a  small  portion  of  the  precipitate  of  ferric  hydroxide  with  anhydrous 
sodium  carbonate  in  the  air  (upon  the  cover  of  a  platinum  crucible);  the  melt 
should  not  have  a  green  color.  (Indicating  no  Cr  present.) 

Mix  the  filtrate  obtained  after  precipitation  of  the  iron,  with  a  little  ammonium 
sulphide  solution;  neither  a  dark  color  nor  a  precipitate  should  appear,  (Indi- 


IRON  SULPHATE  97 


eating  no  Co,  Ni,  etc.  present.)  After  acidulating  the  fluid  with  hydrochloric 
acid,  concentrate,  filter,  evaporate  to  dryness,  and  gently  ignite  the  residue.  After 
complete  volatilization  of  the  ammonium  salts,  dissolve  the  residue  in  hydro- 
chloric acid,  filter  the  solution,  make  alkaline  with  ammonia  water,  and  add 
ammonium  oxalate  solution.  Upon  standing  fifteen  hours  no,  or  only  an  exceed- 
ingly slight,  separation  of  calcium  oxalate  should  occur.  In  the  latter  case 
filter,  wash,  and  ignite  the  precipitate.  The  weight  of  the  calcium  oxide  should 
be  not  more  than  0.001  gm.  (Indicating  not  more  than  0.007  per  cent  Ca.) 

The  fluid  tested  with  ammonium  oxalate  solution  should  exhibit  no  precipi- 
tate within  fifteen  hours  after  the  addition  of  ammonium  phosphate  solution. 
(Indicating  less  than  0.0002  per  cent  Mg.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  the  iron  oxide,  which  has 
been  dried  at  120°  C.,  by  warming  on  the  water-bath  with  10  c.c.  of  fuming 
hydrochloric  acid  and  a  few  drops  of  nitric  acid.  Dilute  the  solution  with  200 
c.c.  of  water,  heat  to  boiling,  and  add  20  c.c.  of  ammonia  water.  Filter  off  the 
precipitate,  wash  free  from  chlorides  with  hot  water,  dry,  ignite,  and  weigh. 

IRON   SULPHATE,  FERROUS 
FeSO4+7H2O.    Mol.  Wt.  278.02 

Pale,  greenish-blue,  monoclinic  crystals,  soluble  in  1.8  parts  of 
cold  water  and  in  0.5  part  of  boiling  water;  insoluble  in  alcohol 

and  in  ether. 

TESTS   OF  PURITY 

Substances  Insoluble  in  Water  (Basic  Iron  Sulphate).  —  The  1  :  20  solution, 
freshly  prepared  with  water  which  has  previously  been  thoroughly  boiled  and  then 
cooled,  should  be  clear  and  have  a  greenish-blue  color.  (Indicating  none  present.) 

Salts  of  the  Alkalies,  Copper,  Zinc.  —  Add  5  c.c.  of  nitric  acid  (sp.gr.  1.3) 
to  a  solution  of  5  gm.  of  ferrous  sulphate  in  100  c.c.  of  water,  and  boil  for  several 
minutes;  then  add  25  c.c.  of  ammonia  water,  filter,  and  bring  the  filtrate  to  a 
volume  of  75  c.c.  by  washing.  The  filtrate  should  be  colorless.  The  ignited 
residue,  from  evaporation  of  50  c.c.  of  the  filtrate,  should  not  exceed  0.001  gm. 
in  weight.  (Indicating  not  more  than  0.03  per  cent  alkali  salts.)  The  remainder 
of  the  filtrate  acidulated  with  acetic  acid,  treated  with  solution  of  potassium  fer- 
rocyanide,  and  allowed  to  stand  two  hours,  should  show  neither  a  white  nor  a 
brownish-red  precipitate.  (Indicating  less  than  0.0036  per  cent  Zn  and  less  than 
0.012  per  cent  Cu.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ferrous  sulphate  in  50  c.c.  of 
well-boiled  water,  add  10  c.c.  of  concentrated  sulphuric  acid,  and  titrate  with 
decinormal  solution  of  potassium  permanganate. 

1  c.c,  of  decinormal  KMnO4  =  0.027802  gm.  of  FeSO4+7H20,  log,  44407. 

IRON   SULPHIDE 

(Ferrous  Sulphide) 
FeS.    Mol.  Wt.  87.91 

Dark  gray  or  grayish-black,  heavy,  hard  lumps  or  sticks,  soluble 
in  diluted  hydrochloric  or  sulphuric  acid  with  the  copious  evolution 
of  hydrogen  sulphide. 


98  CHEMICAL  REAGENTS 


TEST  OF  PURITY 

Quantitative  Determination.  —  Place  0.5  gm.  of  the  finely  powdered  iron 
sulphide  in  a  retort  in  the  tubule  of  which  is  fixed  a  funnel-tube  provided  with  a 
glass  cock.  After  connecting  the  retort  with  a  receiver  containing  50  to  100  c.c. 
of  decinormal  iodine  solution,  allow  to  flow  into  the  retort,  through  the  funnel- 
tube,  a  mixture  of  20  c.c.  of  water  and  20  c.c.  of  dilute  sulphuric  acid;  close 
the  stop-cock,  and  heat  to  boiling.  After  the  decomposition  of  the  iron  sulphide 
is  complete,  and  the  hydrogen  sulphide  has  been  entirely  driven  off  (the  iodine 
solution  must  not  be  fully  decolorized),  determine  the  excess  of  iodine  by  means 
of  decinormal  solution  of  sodium  thiosulphate. 

1  c.c.  of  decinormal  1=0.0043955  gm.  of  FeS,  log.  64301. 

IRON  AND  AMMONIUM   SULPHATE,  FERRIC 
(Ferric  Ammonium  Sulphate;  Ammonio-Ferric  Alum) 
FeNH4(SO4)2+i2H2O.    Mol.  Wt.  482.22 

Pale  violet  (amethyst  colored),  transparent,  octahedral  crystals, 
soluble  in  2  parts  of  water  and  insoluble  in  alcohol.  The  aqueous 
solution  has  an  acid  reaction. 

TESTS  OF  PURITY 

Ferrous  Salt.  —  Dissolve  1  gm.  of  ferric  ammonium  sulphate  in  20  c.c.  of 
water,  and  add  1  c.c.  of  hydrochloric  acid  and  1  drop  of  a  freshly-prepared  solution 
of  potassium  ferricyanide.  Neither  a  green  nor  a  blue  color  should  develop. 
(Indicating  less  than  0.0025  percent  Fe".) 

Chlorides.  —  30  c.c.  of  the  1  :  20  aqueous  solution  should  undergo  no  change 
on  the  addition  of  3  c.c.  of  nitric  acid  and  silver  nitrate  solution.  (Indicating 
less  than  0.0003  per  cent  Cl.) 

Zinc  and  Copper.  —  To  a  solution  of  2  gm.  of  ferric  ammonium  sulphate  in 
50  c.c.  of  water  add  10  c.c.  of  ammonia  water  and  filter.  The  filtrate  should  be 
colorless,  and  upon  acidulating  with  acetic  acid,  adding  solution  of  potassium 
f  errocyanide,  and  allowing  to  stand  two  hours,  neither  a  white  nor  a  brownish-red 
precipitate  should  form.  (Indicating  less  than  0.003  per  cent  Zn  and  less  than 
0.01  per  cent  Cu.) 

Salts  of  the  Alkalies.  —  To  a  solution  of  5  gm.  of  ferric  ammonium  sulphate 
in  100  c.c.  of  water  add  15  c.c.  of  ammonia  water,  filter,  and  evaporate  the  filtrate. 
The  residue  ignited  should  not  exceed  0.002  gm.  in  weight.  (Indicating  not 
more  than  0.04  per  cent.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ferric  ammonium  sulphate 
in  100  c.c.  of  water,  add  2  gm.  of  potassium  iodide  and  5  c.c.  of  hydrochloric 
acid,  allow  to  stand  two  hours  in  a  tightly  closed  flask  and  then  titrate  the  free 
iodine  with  decinormal  solution  of  sodium  thiosulphate. 

1  c.c.  of  decinormal  Na2S2O3  =  0.0482225  gm.  FeNH4(SO4)2+12H20,  log.68325. 

IRON  AND  AMMONIUM   SULPHATE,  FERROUS 

(Ferrous  Ammonium  Sulphate;   Mohr's  Salt) 
FeS04(NH4)2S04+6H20.     Mol.  Wt.  392.16 

Pale,  bluish-green  crystals,  or  light,  bluish-green  crystalline 
powder,  soluble  in  6  parts  of  water.  Ferrous  ammonium  sulphate 


LACMOID  99 


contains  exactly  one-seventh  of  its  weight  of  Fe  in  the  ferrous 

condition. 

TESTS   OF  PURITY 

Ferric  Salts.  —  The  solution  of  1  gm.  of  powdered  ferrous  ammonium  sulphate 
in  20  c.c.  of  boiled  water  with  1  c.c.  of  hydrochloric  acid,  should  not  afford  an 
immediate  red  color  on  adding  a  few  drops  of  potassium  sulphocyanate  solution. 
(Indicating  less  than  0.0008  per  cent  Fe'".) 

Copper,  Zinc,  and  Alkali  Salts.  —  Dissolve  5  gm.  of  ferrous  ammonium  sul- 
phate in  50  c.c.  of  water,  add  5  c.c.  of  nitric  acid  (sp.gr.  1.3),  and  boil  the  solution 
for  a  few  minutes;  then  add  to  the  liquid  15  c.c.  of  ammonia  water,  filter,  and 
bring  the  filtrate  to  a  volume  of  50  c.c.  by  washing.  The  filtrate  must  be  colorless. 

Evaporate  30  c.c.  of  the  filtrate  on  the  water-bath  to  dryness  and  ignite. 
No  weighable  residue  should  remain.  (Indicating  less  than  0.0167  per  cent 
alkali  salts.) 

The  remainder  of  the  filtrate  is  acidulated  with  acetic  acid  and  then  solution 
of  potassium  ferrocyanide  is  added.  Neither  a  white  nor  brownish-red  precipi- 
tate should  appear  on  standing  for  two  hours.  (Indicating  less  than  0.003  per 
cent  Zn  and  less  than  0.01  per  cent  Cu.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  ferrous  ammonium  sulphate 
in  50  c.c.  of  well-boiled  and  cooled  water,  add  10  c.c.  of  diluted  sulphuric  acid, 
and  titrate  with  decinormal  potassium  permanganate  solution. 

1  c.c.  of  decinormal  KMnO4  =  0.039216  gm.  of  FeSO^NH^SOi+eHgO, 
log.  59347. 

LACMOID 
(Resorcinol  Blue) 

Lustrous,  dark-violet  scales  soluble  in  alcohol,  acetone,  and  ether, 
and  but  slightly  soluble  in  water.  The  solution  to  be  used  as  an 
indicator  is  prepared  by  dissolving  0.5  gm.  of  lacmoid  in  100  c.c. 
of  about  85  per  cent  (by  weight)  alcohol,  and  diluting  the  solution 
with  100  c.c.  of  water. 

TEST  OF  SENSITIVENESS 

Add  0.2  c.c.  of  the  above  lacmoid  solution  to  100  c.c.  of  distilled  water  freed 
from  carbon  dioxide  by  prolonged  boiling  in  a  platinum  dish;  the  blue  color  of 
the  water  must  change  to  red  on  the  addition  of  0.05  c.c.  of  decinormal  solution 
of  hydrochloric  acid,  and  the  red  color  should  again  become  blue  on  the  further 
addition  of  0.05  c.c.  of  decinormal  solution  of  potassium  hydroxide. 

NOTE.  —  Regarding  the  use  of  lacmoid  for  the  titration  of  alkaloids  see 
C.  Kippenberger,  Z.  anal.  Chem.,  39,  214  (1900);  abst.,  J.  Chem.  Soc.,  78,  II, 
637  (1900);  J.  Messner,  Z.  angew.  Chem.,  16,  444,  (1903);  abst..  J.  Chem.  Soc., 
84,  II,  519  (1903). 

LEAD  ACETATE 

Pb(C2H3O2)2+3H2O.    Mol.  Wt.  379.20 
Colorless,  translucent,  gradually  efflorescing  crystals  soluble  in 


100  CHEMICAL  REAGENTS 


2.3  parts  of  water.     On  dissolving  in  alcohol  decomposition  .takes 

place. 

TESTS  OF  PURITY 

Earths  and  Alkalies.  —  Dissolve  10  gm.  of  lead  acetate  in  about  200  c.c.  of 
water,  and  precipitate  the  lead  from  the  solution  with  hydrogen  sulphide  gas; 
filter,  evaporate  the  filtrate,  and  ignite  the  residue.  The  weight  of  the  latter 
should  then  not  exceed  0.002  gm.  (Indicating  not  more  than  0.02  per  cent.) 

Copper,  Iron  and  Aluminum.  —  Dissolve  2  gm.  of  lead  acetate  in  10  c.c.  of 
water,  mix  the  solution  with  3  c.c.  of  concentrated  sulphuric  acid,  and  filter. 
On  adding  an  excess  of  ammonia  water  to  the  filtrate  neither  a  precipitate  nor 
a  blue  color  should  appear.  (Indicating  less  than  0.001  per  cent  Cu,  less  than 
0.002  per  cent  Fe,  and  less  than  0.1  per  cent  Al.) 

Lead  Carbonate  and  Substances  Insoluble  in  Water.  —  The  solution  of  5 
gm.  of  lead  acetate  in  50  c.c.  of  freshly  boiled  water  should  be  clear,  or  only 
very  slightly  opalescent.  (Indicating  at  most  a  trace.) 

Chlorides.  —  The  1  :  30  aqueous  solution  acidified  with  nitric  acid  should 
show  no  change  with  silver  nitrate  solution.  (Indicating  less  than  0.0005  per 
cent  Cl.) 

Nitrates.  —  To  the  solution  of  1  gm.  of  lead  acetate  in  10  c.c.  of  water  are  added 
1  drop  of  a  1  :  1000  indigo  solution  and  10  c.c.  of  concentrated  sulphuric  acid; 
the  blue  color  of  the  fluid  should  not  disappear  on  agitation.  (Indicating  less 
than  0.0032  per  cent  N2O5.) 


LEAD   CHROMATE 

PbCrO4.    Mol.  Wt.  323.1 

A  yellowish-brown  powder,  or  brown  lumps,  insoluble  in  water, 
and  ammonia  water;  but  almost  completely  soluble  in  solutions  of 
the  fixed  alkali  hydroxides,  and,  with  decomposition,  almost  wholly 
soluble  also  in  concentrated  nitric  acid. 

TESTS  OF  PURITY 

Substances  Soluble  in  Water.  —  Shake  5  gm.  of  lead  chromate  in  fine  powder 
with  50  c.c.  of  warm  water  (at  about  50°  C.)  for  five  minutes,  then  filter,  evaporate 
the  filtrate,  and  ignite  the  residue.  The  weight  of  the  latter  should  not  exceed 
0.001  gm.  (Indicating  not  more  than  0.02  per  cent.) 

Organic  Substances.  —  Lead  chromate  should  evolve  no  carbon  dioxide  on 
ignition.  (Indicating  none  present.) 

NOTE. — Lead  chromate  which  is  to  be  used  in  the  elementary  analysis  of  organic 
compounds  should  first  be  gently  ignited  in  a  current  of  oxygen,  as  according  to 
C.  H.  L.  Ritthausen,  J.  prakt.  Chem.,  N.  F.,  25,  141  (1882);  dbst.,  J.  Chem. 
Soc.,  42,  898  (1882),  when  ignited  in  air,  it  retains  carbon,  which  can  only  be 
burned  off  by  ignition  in  a  current  of  oxygen, 


LEAD  OXIDE  J  101 

LEAD    OXIDE,    BROWN 

(Lead  Super-,  Di-,  or  Peroxide) 

PbO2.    Mol.  Wt.  239.1 

I 
LEAD   OXIDE,   BROWN,  FREE  FROM  MANGANESE 

A  dark-brown,  amorphous  powder,  insoluble  in  water.  The 
preparation  contains  at  least  95  per  cent  of  PbO«2. 

TESTS   OF  PURITY 

Chlorides.  —  Boil  5  gm.  of  lead  peroxide  with  60  c.c.  of  water  and  5  c.c.  of 
nitric  acid,  filter,  and  to  30  c.c.  of  the  filtrate  add  silver  nitrate  solution.  At 
most  a  slight  opalescent  turbidity  should  appear.  (Indicating  less  than  0.001 
per  cent  Cl.) 

Sulphates.  —  Digest  5  gm.  of  lead  peroxide  with  30  c.c.  of  a  cold  saturated 
aqueous  solution  of  sodium  bicarbonate  for  three  or  four  hours,  shaking  frequently. 
Then  filter,  acidulate  the  filtrate  with  hydrochloric  acid,  boil  the  solution  for  ten 
minutes,  and  add  2  c.c.  of  barium  chloride  solution.  No  precipitate  of  barium 
sulphate  should  form  on  standing  fifteen  hours.  (Indicating  less  than  0.0015 
per  cent  SO3.) 

Substances  Soluble  in  Water  (Lead  Nitrate,  etc.).  —  Boil  2  gm.  of  lead  per- 
oxide with  60  c.c.  of  water,  and  filter;  40  c.c.  of  the  filtrate  should  not  leave  a 
weighable  residue  upon  evaporation  and  ignition.  (Indicating  less  than  0.0375 
per  cent.) 

Calcium  and  Alkalies.  —  Dissolve  2  gm.  of  lead  peroxide  in  25  c.c.  of  hydro- 
chloric acid  and  200  c.c.  of  water,  boil  ten  minutes  to  expel  the  chlorine,  and 
supersaturate  with  hydrogen  sulphide  gas.  Filter  off  the  precipitate,  evaporate 
the  filtrate,  ignite  and  weigh  the  residue.  The  weight  should  not  exceed  0.01 
gm.  (Indicating  not  more  than  0.5  per  cent.) 

Manganese.  —  Heat  5  gm.  of  lead  peroxide  with  10  c.c.  of  concentrated 
sulphuric  acid  until  completely  decomposed.  When  cold,  mix  the  mass  with  20 
c.c.  of  water  and  add  0.5  gm.  of  lead  peroxide.  On  now  warming  again,  the  liquid 
should  not  acquire  a  red  color.  (Indicating  less  0.0002  per  cent  Mn.) 

Quantitative  Determination.  —  Gently  heat  0.5  gm.  of  lead  peroxide  in  a 
porcelain  dish  with  50  c.c.  of  decinormal  solution  of  oxalic  acid  and  25  c.c.  of 
nitric  acid  until  complete  decomposition  has  taken  place.  Now  dilute  with  200 
c.c.  of  water,  heat  the  solution  to  the  boiling-point,  and  allow  decinormal  potas- 
sium permanganate  solution  to  run  into  it  until  the  red  color  imparted  by  1  drop 
of  the  permanganate  solution  no  longer  completely  disappears  within  half  a 
minute. 

1  c.c.  of  decinormal  H2C204  =  0.01 1955  gm,  of  Pb02,  log.  07755, 


I  •  *  ' 

"  "  "*     "  *    »,  N B 


102  CHEMICAL  REAGENTS 


II 

LEAD    OXIDE,    BROWN,    FOR    DENNSTEDT'S   ULTIMATE 

ANALYSIS 

A  dark-brown,  amorphous  powder,  insoluble  in  water,  used  for 
ultimate  organic  analyses  according  to  Dennstedt.* 

TESTS  OF  PURITY 

Chlorides,  Calcium,  and  Alkalies.  —  The  tests  are  to  be  carried  out  as  detailed 
under  Lead  Oxide,  Brown,  Free  from  Manganese. 

Sulphates.  —  Digest  25  gm.  of  lead  peroxide  with  50  c.c.  of  20  per  cent  aqueous 
solution  of  sodium  carbonate  for  one  hour  on  the  water-bath,  shaking  frequently. 
Then  filter,  wash  the  residue  with  50  c.c.  of  hot  water,  acidulate  the  filtrate 
with  hydrochloric  acid,  boil  the  solution  for  ten  minutes,  and  add  2  c.c.  of  barium 
chloride  solution.  No  precipitate  of  barium  sulphate  should  form  on  standing 
fifteen  hours.  (Indicating  less  than  0.0008  per  cent  SO3.) 

Nitrates.  —  Boil  1  gm.  of  lead  peroxide  with  a  mixture  of  5  c.c.  of  diluted 
acetic  acid  and  10  c.c.  of  water,  filter,  and  color  the  filtrate  blue  by  adding  1 
drop  of  a  1  :  1000  indigo  solution.  The  blue  color  should  not  disappear  on  the 
addition  of  10  c.c.  of  concentrated  sulphuric  acid  and  subsequent  agitation. 
(Indicating  less  than  0.0032  per  cent  N2O5.) 

Carbonates.  —  On  pouring  nitric  acid  over  5  gm.  of  lead  peroxide,  no  evolution 
of  gas  should  be  seen,  even  when  observed  through  a  magnifying  glass.  (Indi- 
cating none  present.) 

Quantitative  Determination.  —  This  is  to  be  carried  out  as  detailed  under 
Lead  Oxide,  Brown,  Free  from  Manganese. 

Ill 
LEAD   OXIDE,  BROWN,  GRANULATED 

Lead  peroxide  intended  for  use  in  elementary  analysis,  prepared 
according  to  the  directions  of  Prof.  F.  Pregl.  f 


*  Literature:  M.  Dennstedt,  Z.  anal.  Chem.,  41,  525  (1902);  abst.,  J.  Chem. 
Soc.,  84,  II,  103  (1903);  also:  Anleitung  zur  vereinfachten  Elementaranalyse, 
von  Prof.  Dr.  M.  Dennstedt,  1903.  Published  by  O.  Meissner,  Hamburg. 
M.  Dennstedt,  Chem.  Ztg.,  28,  35  (1904);  abst.,  J.  Chem.  Soc.,  88,  II,  202  (1905). 
H.Hermann,  Z.  anal.  Chem.,  44,  686  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  767 
(1905).  M.  Dennstedt,  Z.  anal.  Chem.,  45,  26  (1906);  dbst.,  J.  Chem.  Soc.,  90, 
II,  398  (1906).  H.  Hermann,  Z.  anal.  Chem.,  45,  236  (1906);  abst.,  J.  Chem. 
Soc.,  90,  II,  200  (1906).  M.  Dennstedt,  Chem.  Ztg.,  33,  769  (1909);  abst.,  J. 
Chem.  Soc.,  96,  II,  759  (1909).  E.  Muller  and  B.  Diethelm,  Z.  angew.  Chem.,  33, 
2118  (1910);  abst.,  J.  Chem.  Soc.,  98,  II,  1110  (1910).  M.  Dennstedt,  Ber.,  41,  600 
(1908);  abst.,  J.  Chem.  Soc.,  94,  II,  321  (1908).  M.  Dennstedt  and  F.  Hassler, 
Chem.  Ztg.,  33,  133  (1909);  abst.,  J.  Chem.  Soc.,  96,  II,  270  (1909).  H.  Weil, 
Ber.,  43,  149  (1910);  abst.,  J.  Chem.  Soc.,  98,  II,  242  (1910).  M.  Dennstedt 
and  F.  Hassler,  Ber.,  43,  1197  (1910);  abst.,  J.  Chem.  Soc.,  98,  II,  547  (1910). 

t  F.  Pregl,  Ber.,  38,  1434  (1905);  abst.,  J.  Chem.  Soc.,  88,  420  (1905). 


LEAD  OXIDE  103 

LEAD  OXIDE,  YELLOW 

(Litharge) 
PbO.    Mol.  Wt.  223.10 

A  yellow  or  reddish-yellow  powder,  almost  insoluble  in  water, 
but  soluble  in  nitric  acid  and  in  potassium  hydroxide  solution. 

TESTS  OF  PURITY 

Substances  Insoluble  in  Acetic  Acid.  —  To  2  gm.  of  lead  oxide  mixed  with  5 
c.c.  of  water  add  10  c.c.  of  diluted  acetic  acid.  No  evolution  of  gas  should  take 
place.  Now  boil  the  liquid  for  several  minutes,  filter  when  cold,  wash  the  undis- 
solved  residue,  dry  at  100°  C.,  and  weigh.  The  weight  should  not  exceed  0.005 
gm.  (Indicating  not  more  than  0.25  per  cent.) 

Carbonates.  —  5  gm.  of  lead  oxide,  when  heated  even  to  the  melting-point, 
should  not  lose  more  than  0.005  gm.  in  weight.  (Indicating  not  more  than  0.1  per 
cent  CO2.) 

Copper,  Iron,  and  Aluminum.  —  Dissolve  2  gm.  of  lead  oxide  in  10  c.c.  of 
nitric  acid  and  5  c.c.  of  water,  add  to  the  clear  solution  3  c.c.  of  concentrated 
sulphuric  acid,  and  filter  off  the  resulting  precipitate.  On  adding  to  the  filtrate 
an  excess  of  ammonia  water,  the  liquid  should  not  acquire  a  blue  color,  nor  should 
a  precipitate  form.  (Indicating  less  than  0.001  per  cent  Cu,  0.002  per  cent  Fe, 
or  0.1  per  cent  Al.) 

Nitrates  and  Nitrites.  —  Mix  1  gm.  of  lead  oxide  with  5  c.c.  of  water,  and 
dissolve  with  the  aid  of  5  c.c.  of  diluted  acetic  acid.  The  blue  color  produced 
by  adding  0.2  c.c.  of  1  :  1000  indigo  solution  should  not  disappear  on  the  addition 
of  10  c.c.  ot  concentrated  sulphuric  acid  and  subsequent  agitation.  (Indicating 
less  than  0.016  per  cent  as  N2O5.) 

Chlorides.  —  The  solution  of  1  gm.  of  lead  oxide  in  5  c.c.  of  nitric  acid  diluted 
with  20  c.c.  of  water  should  not  become  more  than  slightly  opalescent  upon  the 
addition  of  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Earths,  Gypsum,  and  Alkalies.  —  Dissolve  1  gm.  of  lead  oxide  in  10  c.c.  of 
diluted  acetic  acid,  add  50  c.c.  of  water,  and  supersaturate  with  hydrogen  sul- 
phide gas.  Filter  off  the  precipitate,  evaporate  the  filtrate,  ignite  the  residue, 
and  weigh.  The  weight  should  not  exceed  0.003  gm.  (Indicating  not  more 
than  0.3  per  cent.) 


LEAD  SUBACETATE  SOLUTION 

A  clear,  colorless,  liquid,  of  specific  gravity  1.235  to  1.240. 
Lead  subacetate  solution  is  alkaline  to  litmus  paper,  but  does  not 
redden  phenolphthalein. 

TEST  OF  PURITY 

Copper  and  Iron.  —  On  acidifying  10  c.c.  of  lead  subacetate  solution  with  2 
c.c.  of  diluted  acetic  acid,  and  adding  potassium  ferrocyanide  solution,  a  precipitate 
forms  which  should  have  a  pure  white  color.  (Indicating  less  than  0.0006  per 
cent  Cu,  or  less  than  0.0002  per  cent  Fe.) 


104  CHEMICAL  REAGENTS 


LIME,  CHLORINATED 

White  cubes  with  chlorine-like  odor,  and  liberating  chlorine  on 
the  addition  of  hydrochloric  acid.  100  parts  treated  with  hydro- 
chloric acid  should  afford  at  least  25  parts  of  Cl.  Specially  prepared 
in  cube  form  for  the  generation  of  chlorine  in  the  laboratory. 

TEST  OF  PURITY 

The  value  of  this  preparation  depends  entirely  upon  its  active  chlorine. 

Quantitative  Determination.  —  Mix  5  gm.  of  the  powdered  cubes  with  water, 
forming  a  thin  paste.  Wash  this  into  a  500  c.c.  graduated  flask  with  water  and 
dilute  to  the  mark.  To  50  c.c:  of  the  thoroughly  mixed  material  add  a  solution 
of  1  gm.  of  potassium  iodide  in  20  c.c.  of  water,  followed  by  5  c.c.  of  hydrochloric 
acid.  Titrate  the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution, 
of  which  at  least  35.2  c.c.  should  be  required. 

1  c.c.  of  decinormal  Na2S2O3  =  0.003546  gm.  of  Cl,  log.  54974. 

LIME  WATER 

(Solution  of  Calcium  Hydroxide) 

A  clear,  colorless  liquid  having  a  strongly  alkaline  reaction. 
TEST  OF  STRENGTH 

Titrate  100  c.c.  of  lime  water  with  normal  solution  of  hydrochloric  acid,  using 
methyl  orange  as  the  indicator.  Not  less  than  4  c.c.,  nor  more  than  4.5  c.c.  of 
the  normal  solution  of  hydrochloric  acid  should  be  required  to  produce  the  red 
end-point. 

1  c.c/pf  normal  HC1  =  0.037053  gm.  of  Ca(OH)2,  log.  56882. 

LITMUS 

A  specially  purified  dye  obtained  from  various  species  of  lichens. 
It  occurs  in  the  form  of  friable  lumps  consisting  chiefly  of  erythro- 
litmin  and  azolitmin. 

A  large  number  of  formulas  have  been  given  for  the  preparation  of 
litmus  tincture,  of  which  several  are  described  by  Glaser  in  his 
"  Indikatoren  der  Azidimetrie  und  Alkalimetrie." 

A  very  sensitive  litmus  tincture  may  be  prepared  as  follows : 

Dissolve  1  gm.  of  litmus  in  100  c.c.  of  hot  water,  and  add,  drop 
by  drop,  dilute  sulphuric  acid  until  the  liquid  acquires  a  red  color. 
Then  boil  for  ten  minutes  in  order  to  expel  completely  the  carbon 
dioxide.  Should  the  red  color  pass  into  blue  during  the  boiling,  the 
color  is  restored  by  again  adding  dilute  sulphuric  acid.  Now  add 


MAGNESITE  105 

baryta  water,  drop  by  drop,  until  a  violet  color  develops,  set  aside  to 
deposit,  and  filter.  Preserve  the  litmus  tincture  in  bottles  not  com- 
pletely filled,  and  simply  cover  with  a  loose  cap,  or  stopper  with  a 
plug  of  cotton  to  keep  out  the  dust. 

TEST  OF  SENSltlVENESS 

Add  0.2  c.c.  of  litmus  tincture  to  100  c.c.  of  distilled  water,  previously  boiled 
for  some  time  in  a  platinum  dish  to  free  it  from  carbon  dioxide.  The  violet  color 
of  the  liquid  so  obtained  must  change  to  red  on  the  addition  of  0.05  c.c.  of  deci- 
normal  solution  of  hydrochloric  acid;  or  must  pass  into  a  pure  blue  color  on 
the  addition  of  0.05  c.c.  of  decinormal  solution  of  potassium  hydroxide. 

MAGNESITE 
MgC03.    MoLWt.  84.32 

Hard  pieces  about  the  size  of  peas,  soluble  in  hydrochloric  acid 
with  only  a  slight  residue.  It  is  used  for  the  generation  of  carbon 
dioxide,  especially  as  needed  for  the  determination  of  nitrogen  in 

organic  substances. 

TESTS   OF  PURITY 

Loss  on  Ignition.  —  1  gm.  of  magnesite,  powdered  and  then  dried  at  100° 
C.  before  weighing,  should  leave  a  residue  of  about  0.5  gm.  upon  ignition  to 
constant  weight.  (Indicating  about  50  per  cent.) 

Quantitative  Determination.  —  1  gm.  of  magnesite  is  powdered  and  dis- 
solved by  the  aid  of  heat  in  50  c.c.  of  normal  solution  of  sulphuric  acid,  and  the 
solution  is  titrated  with  normal  solution  of  potassium  hydroxide,  using  methyl 
orange  as  indicator. 

1  c.c.  of  normal  H2S04  =  0.04216  gm.  of  MgCO3,  log.  34242. 

MAGNESIA  MIXTURE 

A  solution  prepared  for  the  precipitation  of  phosphoric  acid  in 
quantitative  determinations.  It  contains  110  gm.  of  crystallized 
magnesium  chloride  and  140  gm.  of  ammonium  chloride  in  1300 
gm.  of  water  and  700  gm.  of  ammonia  water. 

MAGNESIUM  CARBONATE 
(Magnesium  Carbonate  Basic) 

White,  light,  loosely  cohering,  easily  friable  masses;  or  white, 
bulky  powder.  Basic  magnesium  carbonate  is  only  very  slightly 
soluble  in  water  free  from  carbon  die  Jde,  yet  it  imparts  to  it  a 
slight  alkaline  reaction.  In  water  impregnated  with  carbon  dioxide 


106  CHEMICAL  REAGENTS 

and  in  aqueous  solutions  of  ammonium  salts,  it  is  easily  soluble. 
The  composition  of  basic  magnesium  carbonate  corresponds  approx- 
imately to  the  formula  4MgCO3  •  Mg(OH)2+6H20.  Mol.  Wt.  503.71 . 
The  content  of  magnesium  is  at  least  24  per  cent. 

TESTS   OF  PURITY 

Substances  Soluble  in  Water.  —  Suspend  3  gm.  of  powdered  basic  magnesium 
carbonate  in  90  c.c.  of  water,  heat  to  boiling,  and  filter  while  hot.  Evaporate 
60  c.c.  of  the  filtrate,  and  weigh  the  residue,  which  should  not  exceed  0.015  gm. 
(Indicating  not  more  than  0.75  per  cent.) 

Sulphates  and  Substances  Insoluble  in  Hydrochloric  Acid.  —  1  gm.  of  the 
basic  magnesium  carbonate  should  entirely  dissolve  in  5  c.c.  of  hydrochloric  acid 
with  15  c.c.  of  water,  and  yield  a  colorless  solution.  (Indicating  no  insoluble 
substances  present.)  On  adding  barium  chloride  solution  to  this  solution  no 
change  should  occur.  (Indicating  less  than  0.0125  per  cent  SO3.) 

Chlorides.  —  Dissolve  1  gm.  of  basic  magnesium  carbonate  in  5  c.c.  of  nitric 
acid  and  15  c.c.  of  water;  on  adding  silver  nitrate  solution,  not  more  than  a  slight 
opalescent  turbidity  should  develop.  (Indicating  less  than  0.002  per  cent  Cl.) 

Barium.  —  The  solution  of  1  gm.  of  basic  magnesium  carbonate  in  5  c.c.  of 
hydrochloric  acid  and  15  c.c,  of  water  should  not  be  rendered  turbid  on  the 
addition  of  diluted  sulphuric  acid.  (Indicating  less  than  0.015  per  cent  Ba.) 

Calcium  and  Alumina.  —  Dissolve  1  gm.  of  basic  magnesium  carbonate  in 
20  c.c.  of  diluted  acetic  acid  and  30  c.c.  of  water.  Boil,  add  20  c.c.  of  ammonia 
water  and  some  ammonium  oxalate  solution.  The  liquid  should  not  become 
turbid  within  five  minutes.  (Indicating  less  than  0.06  per  cent  Ca  and  less 
than  0.6  per  cent  Al.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  basic  magnesium  carbonate  in 
20  c.c.  of  diluted  acetic  acid  and  30  c.c.  of  water  should  be  clear,  and  should 
show  no  change  with  hydrogen  sulphide  water.  (Indicating  none  present.) 

Iron.  —  The  solution  of  0.5  gm.  of  basic  magnesium  carbonate  in  2  c.c.  of 
hydrochloric  acid  and  20  c.c.  of  water  should  not  acquire  a  blue  color  within  one 
minute  after  the  addition  of  0.5  c.c.  of  potassium  ferrocyanide  solution.  (Indi- 
cating less  than  0.015  per  cent  Fe.) 

Quantitative  Determination.  —  On  igniting  1  gm.  of  basic  magnesium  car- 
bonate the  residue  should  weigh  at  least  0.4  gm. 

Dissolve  1  gm.  of  basic  magnesium  carbonate  in  25  c.c.  of  normal  hydrochloric 
acid  solution,  and  titrate  with  normal  potassium  hydroxide  solution,  using  methyl 
orange  as  indicator. 

1  c.c.  of  normal  HC1  =  0.01216  gm.  of  Mg,  log.  08493,  or  0.02016  gm.  of  MgC 
log.  30449. 

MAGNESIUM  CHLORIDE 

MgCl2+6H2O.    Mol.  Wt.  203.34 

White,  deliquescent,  crystals  soluble  in  about  0.6  part  of  cold, 
or  in  0.3  part  of  hot,  water,  and  in  5  parts  of  85  per  cent  alcohol.  The 
aqueous  solution  is  neutral  to  litmus  paper. 

TESTS  OF  PURITY 

Substances  Insoluble  in  Alcohol.  —  2  gm.  of  magnesium  chloride  should 
completely  dissolve  in  10  c.c.  of  85  per  cent  alcohol,  and  yield  a  clear  solution. 
(Indicating  none  present.) 


gm. 
No 


MAGNESIUM  OXIDE  107 


Sulphates.  —  The  solution  of  1  gm.  of  magnesium  chloride  in  20  c.c.  of  water 
should  not  be  changed  on  the  addition  of  1  c.c.  of  hydrochloric  acid  and  barium 
chloride  solution.  (Indicating  less  than  0.01  per  cent  SO3.) 

Phosphates  and  Arsenates.  —  Dissolve  3  gm.  of  magnesium  chloride  and  6 

.  of  ammonium  chloride  in  24  c.c.  of  water,  and  add  12  c.c.  of  ammonia  water. 
o  turbidity  or  precipitate  should  form  on  standing  fifteen  hours.  (Indicating 
less  than  0.0016  per  cent  P2O5,  and  less  than  0.05  per  cent  As2O5.) 

Ammonium  Salts.  —  On  heating  3  gm.  of  magnesium  chloride  with  10  c.c. 
of  sodium  hydroxide  solution  (sp.gr.  1.3),  no  vapors  of  ammonia  should  be  evolved 
(to  be  ascertained  by  moistened  litmus  paper).  (Indicating  less  than  0.0011 
per  cent  NH3.) 

Barium.  —  The  solution  of  1  gm.  of  magnesium  chloride  in  20  c.c.  of  water 
should  afford  no  reaction  on  the  addition  of  diluted  sulphuric  acid.  (Indicating 
less  than  0.002  per  cent  Ba.) 

Heavy  Metals  and  Calcium.  —  (a)  The  solution  of  1  gm.  of  magnesium  chloride 
in  20  c.c.  of  water  must  not  be  affected  by  hydrogen  sulphide  water.  (Indi- 
cating no  heavy  metals  present.) 

(b)  Dissolve  1  gm.  of  magnesium  chloride  in  20  c.c.  of  water,  and  add  1  gm. 
of  ammonium  chloride  and  5  c.c.  of  ammonia  water;  no  change  should  occur  on 
the  further  addition  of  ammonium  oxalate  solution  (indicating  less  than  0.005 
per  cent  Ca),  nor  with  a  few  drops  of  ammonium  sulphide  solution.  (Indi- 
cating no  heavy  metals  present.) 

MAGNESIUM    OXIDE 

(Magnesia) 
MgO.    Mol.  Wt.  40.32 

I 
MAGNESIUM   OXIDE 

A  white,  light,  fine  powder,  almost  insoluble  in  water.  The 
preparation  contains  at  least  88  per  cent  of  magnesium  oxide. 

TESTS  OF  PURITY 

Substances  Soluble  in  Water.  —  Heat  3  gm.  of  magnesium  oxide  with  90  c.c. 
of  water  to  boiling,  and  filter  hot.  The  filtrate  should  have  at  most  a  slight 
alkaline  reaction,  and  on  evaporating  60  c.c.  the  weight  of  the  residue  should 
not  exceed  0.015  gm.  (Indicating  not  more  than  0.75  per  cent.) 

Sulphates  and  Substances  Insoluble  in  Hydrochloric  Acid.  —  1  gm.  of  mag- 
nesium oxide  should  completely  dissolve  in  10  c.c.  of  hydrochloric  acid  and  10 
c.c.  of  water,  yielding  a  clear  solution.  (Indicating  no  insoluble  substances 
present.)  This  solution  should  not  be  rendered  turbid  within  one  minute  after 
the  addition  of  barium  nitrate  solution.  (Indicating  less  than  0.375  per  cent  SO3.) 

Chlorides.  —  The  solution  of  0.5  gm.  of  magnesium  oxide  in  10  c.c.  of  nitric 
acid  and  10  c.c.  of  water  should  not  become  more  than  opalescent  on  the  addition 
of  silver  nitrate  solution.  (Indicating  less  than  0.010  per  cent  CL) 

Carbonates.  —  Heat  0.5  gm.  of  magnesium  oxide  with  10  c.c.  of  water,  and 
pour  this  mixture  into  10  c.c.  of  dilute  acetic  acid.  Solution  should  take  place 
without  any  effervescence;  only  a  slight  evolution  of  gas  may  occur.  (Indicating 
less  than  4  per  cent  CO2.) 


108  CHEMICAL  REAGENTS 


Nitrogen.  —  To  the  solution  of  10  gm.  of  magnesium  oxide  in  100  c.c.  of  hydro- 
chloric acid  and  50  c.c.  of  water  add  2  gm.  of  Devarda's  metal  and  allow  the 
mixture  to  stand,  with  frequent  rotation,  until  the  evolution  of  hydrogen  has 
ceased.  When  the  mixture  is  cold,  add  100  c.c.  of  sodium  hydroxide  solution 
(N-free,  sp.gr.  1.3)  and  distil  off  about  70  c.c.,  collecting  the  distillate  in  a 
receiver  containing  2  to  3  c.c.  of  fifth-normal  solution  of  hydrochloric  acid  and 
10  c.c.  of  water.  Titrate  the  distillate  with  fifth-normal  solution  of  potassium 
hydroxide,  using  methyl  orange  as  indicator.  Not  more  than  0.2  c.c.  of  the 
fifth-normal  solution  of  hydrochloric  acid  should  be  required  to  neutralize  the 
ammonia  obtained  from  the  magnesium  oxide.  (Indicating  not  more  than 
0.0056  per  cent  N.) 

Barium.  —  The  solution  of  1  gm.  of  magnesium  oxide  in  10  c.c.  of  hydro- 
chloric acid  and  10  c.c.  of  water  should  not  be  rendered  turbid  on  the  addition 
of  diluted  sulphuric  acid.  (Indicating  less  than  0.02  per  cent  Ba.) 

Calcium.  —  On  shaking  1  gm.  of  magnesium  oxide  with  20  c.c.  of  water  and 
filtering,  the  filtrate,  on  the  addition  of  ammonium  oxalate  solution,  should  not 
exhibit  more  than  an  opalescent  turbidity  within  five  minutes.  (Indicating  less 
than  0.01  per  cent  Ca.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  magnesium  oxide  in  20  c.c.  diluted 
acetic  acid  and  30  c.c.  of  water  should  not  be  affected  by  hydrogen  sulphide 
water.  (Indicating  none  present.) 

Iron.  —  The  solution  of  0.2  gm.  of  magnesium  oxide  in  2  c.c.  of  hydrochloric 
acid  and  8  c.c.  of  water  should  not  acquire  a  blue  color  within  one  minute  after 
the  addition  of  0.5  c.c.  of  potassium  ferrocyanide  solution.  (Indicating  less 
than  0.025  per  cent  Fe.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  magnesium  oxide  in  30 
c.c.  of  normal  solution  of  hydrochloric  acid  and  titrate  with  normal  solution  of 
potassium  hydroxide,  using  methyl  orange  as  indicator. 

1  c.c.  normal  HC1  =  0.02016  gm.  MgO,  log.  30449. 

II 

MAGNESIUM   OXIDE,  FREE  FROM  SULPHATES 

TESTS  OF  PURITY 

The  tests  as  given  for  Magnesium  Oxide  should  be  made  upon  this  article 
and  in  addition  the  following  one: 

Sulphates.  —  Dissolve  3  gm.  of  magnesium  oxide  in  20  c.c.  of  hydrochloric 
acid,  dilute  the  solution  to  about  100  c.c.,  boil  a  few  minutes,  and  add  barium 
chloride  solution.  No  precipitate  of  barium  sulphate  should  form  within  fifteen 
hours.  (Indicating  less  than  0.016  per  cent  SO3.) 

MAGNESIUM   SULPHATE 
MgSO4+7H2O.     Mol.  Wt.  246.50 

Small,  colorless,  prismatic  crystals,  only  very  slightly  efflorescent 
in  air.  Soluble  in  1  part  of  cold,  and  in  0.3  part  of  boiling,  water, 
but  insoluble  in  alcohol.  The  aqueous  solution  is  neutral  to  litmus 
paper. 


MAGNESIUM  AND  AMMONIUM  CHLORIDE  109 


TESTS   OF  PURITY 

Chlorides.  —  Dissolve  1  gm.  of  magnesium  sulphate  in  20  c.c.  of  water,  and 
add  1  c.c.  of  nitric  acid;  the  solution  should  not  be  affected  by  silver  nitrate 
solution.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Phosphates,  Arsenates,  and  Heavy  Metals.  —  The  tests  are  to  be  carried  out 
as  detailed  under  Magnesium  Chloride. 

Iron.  —  20  c.c.  of  the  1  :  20  aqueous  solution,  slightly  acidified  with  nitric 
acid  and  boiled,  should  not  show  a  red  color  on  the  addition  of  potassium  sulpho- 
cyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Arsenic.  —  A  mixture  of  1  gm.  of  powdered  magnesium  sulphate  and  3  c.c. 
of  stannous  chloride  solution  should  not  acquire  a  dark  color  on  standing  one 
hour.  (Indicating  less  than  0.0015  per  cent  As.) 


MAGNESIUM  AND  AMMONIUM   CHLORIDE 
MgCl2NH4Cl+6H2O.     Mol.  Wt.  256.84 

Rhombic  crystals,  or  white,  crystalline  powder,  easily  soluble  in 
water.  Its  principal  use  is  in  the  preparation  of  magnesia  mixture 
for  the  determination  of  phosphoric  acid. 

TESTS  OF  PURITY 

Sulphates;  Heavy  Metals;  Calcium  and  Barium.  —  The  tests  are  to  be  made 
as  detailed  under  Magnesium  Chloride. 

Phosphates  and  Arsenates.  —  Dissolve  5  gm.  of  magnesium  and  ammonium 
chloride  in  10  c.c.  of  water,  and  add  5  c.c.  of  ammonia  water.  No  turbidity  or 
precipitate  should  form  within  fifteen  hours.  (Indicating  less  than  0.001  per 
cent  P2O5,  and  less  than  0.005  per  cent  As2O5.) 


MANGANESE  CHLORIDE 

(Manganous  Chloride) 
MnCl2+4H2O.     Mol.  Wt.  197.91 

Reddish,  hygroscopic  crystals,  easily  soluble  in  water  (about  1  :  1) 
and  also  soluble  in  alcohol. 

TESTS  OF  PURITY 

Sulphates.  —  Dissolve  1  gm.  of  manganous  chloride  in  10  c.c.  of  water,  add 
1  c.c.  of  hydrochloric  acid  and  some  barium  chloride  solution.  No  change  should 
be  noticeable.  (Indicating  less  than  0.01  per  cent  SOs.) 

Chlorine.  —  The  solution  of  1  gm.  of  manganous  chloride  in  40  c.c.  of  water 
and  5  c.c.  of  16  per  cent  sulphuric  acid  should  not  be  rendered  blue  within  one 
minute  by  zinc  iodide-starch  solution.  (Indicating  less  than  0.0023  per  cent  Cl.) 

Calcium.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should  not  be  rendered  turbid 


110  CHEMICAL  REAGENTS 


within  one  minute  after  the  addition  of  2  c.c.  of  ammonium  oxalate  solution.* 
(Indicating  less  than  0.03  per  cent  Ca.) 

Iron.  —  Dissolve  1  gm.  of  manganous  chloride  in  15  c.c.  of  water,  add  1  c.c. 
of  hydrochloric  acid,  3  c.c.  of  chlorine  water,  and  heat  to  boiling.  The  solution, 
when  cold,  should  not  acquire  a  red  color  on  the  addition  of  potassium  sulpho- 
cyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Salts  of  Magnesium  and  the  Alkalies.  —  Precipitate  the  manganese  from  a 
solution  of  3  gm.  of  manganous  chloride  in  50  c.c.  of  water  by  adding  ammonium 
carbonate  solution  (5  gm.  of  ammonium  carbonate  in  50  c.c.  of  water).  Filter, 
evaporate  the  filtrate,  and  ignite  the  residue.  It  should  not  weigh  more  than 
0.001  gm.  (Indicating  not  more  than  0.033  per  cent.) 

Zinc.  —  Dissolve  1  gm.  of  manganous  chloride  and  1  gm.  of  sodium  acetate 
in  10  c.c.  of  water,  and  add  a  few  drops  of  acetic  acid  and  hydrogen  sulphide 
water.  No  white  precipitate  soluble  in  hydrochloric  acid  should  form.  (Indi- 
cating less  than  0.2  per  cent  Zn.) 

>•  Other  Foreign  Metals.  —  Dissolve  1  gm.  of  manganese  chloride  in  20  c.c.  of 
water  and  add  5  c.c.  of  hydrochloric  acid.  This  solution  should  not  be  affected 
by  hydrogen  sulphide  water.  (Indicating  none  present.) 

MANGANESE  DIOXIDE 
(Manganese  Per-  or  Super-Oxide;  Pyrolusite) 
MnO2.    Mol.  Wt.  86.93 

Grayish-black  pieces,  soluble  in  cold,  concentrated  hydrochloric 
acid  forming  manganese  tetrachloride,  which  on  heating  decomposes 
into  manganous  chloride  and  chlorine.  In  hot,  concentrated  sul- 
phuric acid  manganese  dioxide  dissolves  with  the  evolution  of  oxygen. 

TEST  OF  PURITY 

Quantitative  Determination.!  —  Weigh  off  1.0866  gm.  of  the  manganese 
dioxide,  previously  very  finely  powdered  and  dried  to  constant  weight  at  100° 
C.  Place  in  a  flask  provided  with  a  Bunsen  rubber  valve,  and  add  75  c.c.  (3 
pipettefuls  of  25  c.c.  each)  of  a  solution  of  100  gm.  of  pure,  crystallized  ferrous 
sulphate  and  100  c.c.  of  pure,  concentrated  sulphuric  acid  in  1000  c.c.  of  water.  J 
Close  the  flask  with  the  stopper  bearing  the  Bunsen  valve,  and  heat  until  the 
manganese  dioxide  is  completely  decomposed,  leaving  no  dark-colored  residue. 
Then  cool,  making  sure  the  valve  is  closed  as  indicated  by  the  collapsing  of  the 
rubber  tubing. 

When  cold,  dilute  with  200  c.c.  of  water,  and  titrate  with  seminormal  potas- 
sium permanganate  solution  until  the  faint  red  color  no  longer  disappears,  but 
persists  for  half  a  minute  (further  decoloration  is  neglected).  From  the  quantity 
of  permanganate  solution  corresponding  by  calculation  to  the  75  c.c.  of  ferrous 
sulphate  solution  deduct  now  the  quantity  of  permanganate  solution  actually 
used.  Each  cubic  centimeter  of  the  difference  represents  0.02173  gm.,  or  2 
per  cent,  of  MnC>2. 


*  On  allowing  this  mixture  to  stand  for  some  time,  manganous  oxalate  sepa- 
rates in  the  form  of  acicular  crystals. 

t  Lunge,  Chem.-Tech.  Untersuch.-Meth.,  5  ed.,  I,  486. 

t  This  ferrous  sulphate  solution  is  standardized  against  seminormal  potassium 
permanganate  solution  on  the  same  day,  using  the  same  pipette. 


MANGANESE  SULPHATE  111 


MANGANESE  METAPHOSPHATE  SOLUTION 

A  reagent  for  the  detection  of  albumin,  prepared  as  directed  by 
L.  Blum.* 

The  solution  should  have  a  pink  color.  If  in  the  course  of  time 
it  becomes  colorless,  it  is  no  longer  of  use  as  a  $eagent  for  albumin. 

MANGANESE   SULPHATE 

(Manganous  Sulphate) 
MnSO4+4H2O.    Mol.  Wt.  223.06. 

Pale-red,  monoclinic  crystals,  soluble  in  0.8  part  of  water,  and 
insoluble  in  alcohol.     The  aqueous  solution  is  neutral  to  litmus  paper. 
TESTS   OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  manganese  sulphate  in  20  c.c.  of  water 
should  not  be  rendered  more  than  slightly  opalescent  on  the  addition  of  1  c.c. 
of  nitric  acid,  followed  by  silver  nitrate  solution.  (Indicating  less  than  0.002 
per  cent  Cl.) 

Substances  Reducing  Potassium  Permanganate.  —  Dissolve  15  gm.  of  man- 
ganese sulphate  in  200  c.c.  of  water  with  3  c.c.  each  of  phosphoric  acid  (sp.gr. 
1.7)  and  concentrated  sulphuric  acid.  Not  more  than  0.1  c.c.  of  decinormal 
potassium  permanganate  solution  should  be  necessary  to  impart  a  slight  red 
color  to  the  solution.  (Indicating  at  most  a  trace  present  ) 

Calcium,  Iron,  Zinc,  Other  Foreign  Metals,  and  Salts  of  Magnesium  and  the 
Alkalies.  —  The  tests  are  carried  out  as  detailed  under  Manganese  Chloride. 

MERCURY 

Hg.    Atomic  Wt.  200.6 

A  liquid,  silver-white  metal,  which  solidifies  at  about  —39°  C., 
and  boils  at  about  357°  C.  Its  specific  gravity  is  13.56. 

TESTS   OF  PURITY 

Foreign  Metals.  —  (a)  Mercury  should  have  a  bright  surface  which  should 
not  be  affected  by  shaking  with  pure  air.  (Indicating  none  present.) 

(6)  On  heating  20  gm.  of  mercury  in  a  porcelain  dish  under  a  good  draft, 
no  weighable  residue  should  remain.  (Indicating  less  than  0.0025  per  cent.) 

(c)  On  boiling  5  gm.  of  mercury  with  5  c.c.  of  water  and  4.5  gm.  of  sodium 
thiosulphate  for  about  one  minute,  in  a  test-tube,  the  mercury  must  not  lose 
its  luster,  and  should  acquire  at  most  only  a  slight  yellowish  tinge.     (Indicating 
at  most  a  trace  present.) 

(d)  Mercury  should    dissolve   completely  in  nitric  acid.      (Indicating  no 
insoluble  metals  present.) 

*  L.Blum,  Chem.  Ztg.,  11  (Rep.),  24  (1887);  abst.,  J.  Chem.  Soc.,  52,  1003 

(1887). 


112  CHEMICAL  REAGENTS 

MERCURY  BICHLORIDE 

(Mercuric  Chloride;  Corrosive  Sublimate) 
HgCl2.    Mol.  Wt.  271.52 

White,  translucent,  prismatic  crystals.  Mercuric  chloride  is 
soluble  in  16  parts  of  cold,  and  in  3  parts  of  boiling,  water;  in  3 
parts  of  alcohol  (about  85  per  cent  by  weight),  and  in  about  17  parts 
of  ether*  (sp.gr.  0.720).  The  aqueous  solution  is  acid  to  litmus 
paper;  addition  of  sufficient  sodium  chloride  effects  neutrality. 

TESTS   OF  PURITY 

Foreign  Matter  not  Precipitated  by  Hydrogen  Sulphide.  —  Dissolve  5  gm. 
of  mercuric  chloride  in  100  c.c.  of  water,  add  5  c.c.  of  hydrochloric  acid,  and  pass 
into  the  solution  hydrogen  sulphide  gas  until  the  mercury  has  been  completely 
precipitated.  Then  filter,  evaporate  the  filtrate  to  dryness  on  the  water-bath, 
and  ignite  gently.  No  weighable  residue  should  remain.  (Indicating  less  than 
0.01  per  cent.) 

Arsenic.  —  Shake  the  mercury  sulphide  obtained  in  the  above  test  with  a 
mixture  of  5  c.c.  of  ammonia  water  and  45  c.c.  of  water,  filter,  and  acidulate 
the  filtrate  with  hydrochloric  acid.  Neither  a  yellow  color  nor  a  yellow  precipitate 
should  appear.  (Indicating  less  than  0.008  per  cent  As.) 

Mercurous  Chloride  and  Other  Substances  Insoluble  in  Ether.  —  1  gm.  of 
powdered  mercuric  chloride  should  be  completely  soluble  in  25  c.c.  of  ether. 
(Indicating  none  present.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  mercuric  chloride  in  100 
c.c.  of  water  and  titrate f  the  solution  with  semi-normal  solution  of  potassium 
cyanide,  using  phenolphthalein  as  indicator. 

1  c.c.  of  seminormal  KCN  =  0.06788  gm.  HgCl2,  log.  83174. 

MERCURY  NITRATE 

(Mercurous  Nitrate) 
HgN03+H20.    Mol.  Wt.  280.63 

Colorless,  monoclinic  tables  or  prisms,  soluble  in  about  2  parts  of 
warm  water,  affording  a  solution  with  an  acid  reaction.  On  the 
addition  of  much  water  the  solution  is  decomposed  with  the  separation 
of  a  light-yellow  precipitate.  Solution  is  best  effected  by  means  of 
water  acidified  with  nitric  acid. 


*  The  extent  of  solubility  of  mercuric  chloride  in  ether  depends  upon  the 
alcohol  content  of  the  ether. 

tE.  Rupp,  Apotheker-Zeitung,  24,   939  (1909);  dbst.,  C.  A.,  4,  1084  (1910). 


MERCURY  OXIDE  RED  113 


TESTS   OF  PURITY 

Non-volatile  Matter.  —  On  igniting  2  gm.  of  mercurous  nitrate,  no  weighable 
residue  should  remain.  (Indicating  less  than  0.025  per  cent.) 

Mercuric  Salts.  — •  Dissolve  1  gm.  of  mercurous  nitrate  in  5  c.c.  of  -vater 
with  3  to  5  drops  of  nitric  acid.  Dilute  the  solution  with  15  c.c.  of  water,  add  1 
c.e.  of  hydrochloric  acid,  filter,  and  add  hydrogen  sulphide  water  to  the  nitrate. 
More  than  traces  of  a  precipitate  should  not  be  visible.  (Indicating  at  most  a 
trace  present.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  mercurous  nitrate  in  25  c.c. 
of  nitric  acid  in  a  100  c.c.  graduated  flask,  add  decinormal  potassium  permanga- 
nate solution  until  the  mixture  acquires  a  red  color  lasting  several  minutes, 
or  until  the  separation  of  brown  flocks,  and  then  add  powdered  ferrous  sulphate 
until  the  solution  is  clear  and  decolorized.  Fill  to  the  mark  with  water,  mix, 
and  titrate  of  20  c.c.  of  the  solution  with  decinormal  ammonium  sulphocyanate 
solution,  after  the  addition  of  5  c.c.  of  a  cold  saturated  solution  of  ferric-ammonium 
sulphate. 

1  c.c.  of  decinormal  NH4CNS  =  0.01403125  gm.  HgNO3+H20,  log.  14710, 


MERCURY  OXIDE  RED 

(Mercuric  Oxide  Red) 

HgO.    Mol.  Wt.  216.6 

A  yellowish-red,  crystalline  powder,  almost  insoluble  in  water, 
easily  soluble  in  diluted  nitric  acid,  forming  a  clear  solution,  and  in 
diluted  hydrochloric  acid,  forming  a  solution  at  most  slightly  turbid. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  On  igniting  2  gm.  of  mercuric  oxide,  no  weighable 
residue  should  remain.  (Indicating  less  than  0.025  per  cent.) 

Chlorides.  —  The  solution  of  1  gm.  of  mercuric  oxide  in  5  c.c.  of  nitric  acid 
and  15  c.c.  of  water  should  not  be  rendered  more  than  slightly  opalescent  on 
adding  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Sulphates.  —  The  solution  of  1  gm.  of  mercuric  oxide  in  5  c.c.  of  nitric  acid 
and  15  c.c.  of  water  should  show  no  change  on  the  addition  of  barium  nitrate 
solution.  (Indicating  less  than  0.175  per  cent  SO3.) 

Nitrates.  —  Dissolve  1  gm.  of  mercuric  oxide  in  2  c.c.  of  water  and  2  c.c.  of 
concentrated  sulphuric  acid,  and  overlay  this  mixture,  when  cold,  with  ferrous 
sulphate  solution.  No  colored  zone  should  form  at  the  plane  of  contact  of  the 
two  layers.  (Indicating  less  than  0.016  per  cent  N2O5.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  the  mercuric  oxide  in  25 
c.c.  of  nitric  acid  in  a  100  c.c.  graduated  flask,  and  dilute  with  water  to  the  mark. 
Titrate  20  c.c.  of  this  solution  with  decinormal  solution  of  ammonium  sulphocy- 
anate, using  5  c.c.  of  cold,  saturated  solution  of  ferric-ammonium  sulphate  as 
indicator. 

1  c.c.  of  decinormal  NH4CNS= 0.01083  gm.  of  HgO,  log.  03463. 


114  CHEMICAL  REAGENTS 

MERCURY  OXIDE  YELLOW 

(Mercuric  Oxide  Yellow) 
HgO.    Mol.  Wt;  216.6. 

A  yellow,  amorphous  powder,  almost  insoluble  in  water,  but 
easily  soluble  in  diluted  nitric  or  hydrochloric  acid.  On  being  shaken 
with  oxalic  acid  solution,  yellow  mercuric  oxide  changes  gradually 
into  a  white  crystalline  powder. 

TESTS   OF  PURITY 

The  tests  for  non-volatile  matter,  chlorides,  sulphates,  and  nitrates,  and  the 
quantitative  determination  are  to  be  carried  out  as  detailed  under  Mercury 
Oxide  Red. 

MERCURY  AND  POTASSIUM  IODIDE 
(Mercuric  Potassium  Iodide) 

HgI22KI.    Mol.  Wt.  786.48 
Sulphur-yellow,  crystalline  pieces,  deliquescent  in  moist  air. 

TEST  OF  PURITY 

Solubility.  —  5  gm.  of  mercuric  potassium  iodide  should  completely  dissolve 
in  10  c.c.  of  water,  and  yield  a  clear  solution  which  should  remain  clear  even 
after  adding  80  c.c.  of  water. 

METAPHENYLENEDIAMINE  HYDROCHLORIDE 

(Metadiaminobenzene  Hydrochloride) 
C6H4(NH2)22HC1.    Mol.  Wt.  181.02 

A  white,  or  slightly  reddish-white,  crystalline  powder,  easily 
soluble  in  water.  Metaphenylenediamine  hydrochloride  is  used  as  a 
reagent  in  the  form  of  a  1  :  200  solution.  Should  this  solution  have  a 
color,  it  is  to  be  decolorized  before  using  by  heating  with  previously 
ignited  animal  charcoal. 

TESTS  OF  PURITY 

Inorganic  Impurities.  —  On  igniting  1  gm.  of  metaphenylenediamine  hydro- 
chloride  no  weighable  residue  should  remain.  (Indicating  less  than  0.05  per  cent.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  metaphenylenediamine 
hydrochloride  in  50  c.c.  of  85  per  cent  alcohol  in  a  glass-stoppered  flask,  and  titrate 
this  solution  with  normal  potassium  hydroxide  solution,  using  Poirrier's  blue  as 
indicator. 

1  c.c.  of  normal  KOH  =  0.09051  gm.  of  C6H4(NH2)2-2HC1,  log.  95670. 


METHYL  ORANGE  115 

METHYL  ORANGE 

(Sodium  Salt  of  Paradimethylaminoazobenzenesulphonic  Acid) 
(CH3)2NC6H4N:  NC6H4SO3Na.     Mol.  Wt.  327.21 

An  orange-yellow  powder,  easily  soluble  in  water.  As  an  indi- 
cator, a  solution  of  0.1  gm.  in  100  c.c.  of  water  is  used. 

TEST  OF  SENSITIVENESS 

To  100  c.c.  of  distilled  water  in  a  Jena  flask  add  1  drop  of  the  above  methyl 
orange  solution.  On  adding  to  this  solution  0.05  c.c.  of  decinormal  solution  of 
hydrochloric  acid,  the  light  yellow  color  of  the  water  should  change  to  a  red, 
and  on  the  further  addition  of  0.05  c.c.  of  decinormal  solution  of  potassium 
hydroxide  the  original  color  should  be  restored. 

METHYL  RED 

(Methyl  Red  Indicator) 

(CH3)2NC6H4N:  NC6H4COOH.    Mol.  Wt.  269.15 

Glistening,  violet  crystals,  almost  insoluble  in  water,  soluble  in 
alcohol  and  in  glacial  acetic  acid.  As  an  indicator,  a  solution  of 
0.2  gm.  in  100  c.c.  of  alcohol  is  used. 

TEST  OF  SENSITIVENESS 

Mix  1  or  2  drops  of  methyl  red  solution  with  100  c.c.  of  water  which  has 
been  freed  from  carbon  dioxide  by  long  boiling  in  a  platinum  dish.  The  yellowish- 
red  color  of  the  mixture  should  be  changed  to  yellow  by  the  addition  of  0.05 
c.c.  of  centinormal  potassium  hydroxide  solution,  and  on  further  adding  0.1  c.c. 
of  centinormal  hydrochloric  acid  solution  the  fluid  should  become  red. 

NOTE.  —  Regarding  the  use  of  methyl  red  as  an  indicator,  see  E.  Rupp  and 
R.  Loose,  Ber.,  41,  3905  (1908);  abst.,  J.  Chem.  Soc.,  96,  II,  90  (1909).  Tizard, 
J.  Chem.  Soc.,  97,  II,  2477  (1910). 

NITROBENZALDEHYDE.   ORTHO- 

C6H4(NO2)CHO.     Mol.  Wt.  151.05 

Light-yellow  needles,  melting  between  45°  and  46°  C.,  and  easily 
soluble  in  alcohol  and  in  ether. 


116  CHEMICAL  REAGENTS 


NITRON 
FOR  THE  GRAVIMETRIC  DETERMINATION  OF  NITRIC  ACID 

(1.4  Diphenyl  -  3.5  Endanilodihydrotriazol) 
C2oH16N4.    Mol.  Wt.  312.17 

Shining,  yellow  leaflets,  or  amorphous  powder,  melting  at  189°  C. 
with  decomposition.  It  is  soluble  in  alcohol,  chloroform,  acetone, 
and  ethyl  acetate,  difficultly  soluble  in  ether,  and  insoluble  in  water. 
In  alcohol,  the  substance  undergoes  partial  decomposition,  indicated 
by  the  red  color  of  the  solution.  Nitron  is  used  as  a  reagent  in  the 
form  of  a  10  per  cent  solution  in  5  per  cent  acetic  acid,  according  to 
the  method  of  M.  Busch.  This  solution  should  be  kept  in  well- 
stoppered  bottles  and  protected  from  light. 

TEST  OF  PURITY 

Solubility. — 1  gm.  of  nitron  should  easily  and  almost  completely  dissolve 
in  10  c.c.  of  5  per  cent  acetic  acid. 

NOTE.  —  Literature:  M.  Busch,  "Gravimetric  Determination  of  Nitric 
Acid",  Ber.,  38,  861  (1905);  abst.,  J.  Chem.  Soc.,  88,  II,  282  (1905).  C.Paaland 
E.  Weidenkaff,  "  Determination  of  Nitric  Acid  in  Organic  Salts,"  Ber.,  38,  1688 
(1905);  abst.,  J.  Chem.  Soc.,  88,  I,  436  (1905).  M.  Busch,  "  Determination  of 
Nitric  Acid  in  Water,"  Z.  Nahr.  Genussm.,  9,  464  (1905);  abst.,  J.  Chem.  Soc., 
90,  II,  282  (1905).  A.  Gutbier,  "  Gravimetric  Determination  of  Nitric  Acid  by 
Means  of  Nitron  ace.  to  M.  Busch"  Z.  angew.  Chem.,  18,  494  (1905);  abst., 
J.  Chem.  Soc.,  88,  II,  418  (1905).  G.  Lunge  and  E.  Berl,  "  Analysis  of  Mixed 
Acids  (Sulphuric  and  Nitric  Acids)",  Z.  angew.  Chem.,  18,  1681  (1905);  abst., 
J.  Chem.  Soc.,  90,  II,  49  (1906).  M.  Busch,  "  Determination  of  Nitrate  in  the 
Presence  of  Nitrite,"  Ber.,  39,  1401  (1906);  abst.,  J.  Chem.  Soc.,  90,  II,  392 
(1906).  Compare  W.  Traube  and  A.  Biltz,  Ber.,  39,  168  (1906);  abst.,  J.  Chem. 
Soc.,  90,  II,  159  (1906).  M.  Busch,  "  A  New  Method  for  the  Determination  of 
the  Nitrogen-content  of  Nitrocellulose,"  Z.  angew.  Chem.,  30,  1329  (1906)  [or  Z. 
ges.  Schiess-Sprengstoffw.,  1,  232  (1906)];  abst.,  J.  Chem.  Soc.,  90,  II,  708  (1906). 
C.  Paal  and  G.  Mehrtens,  "  Gravimetric  Determination  of  Saltpeter  in  Meat," 
Z.  Nahr.  Genussm.,  12,  410  (1906);  abst.,  J.  Chem.  Soc.,  90,  II,  898  (1906).  H. 
L.  Visser,  "  The  Use  of  Nitron  in  Microchemical  Analysis,"  Chem.  Weekblad, 
3,  743  (1906);  abst.,  Chem.  Zentr.,  (5)  11,  302  (1907);  abst.,  J.  Chem.  Soc.,  92,  II, 
394  (1907).  J.  Litzendprff,  "  The  Use  of  Nitron  for  the  Determination  of 
Nitric  Acid  in  Soil  and  in  Plants,"  Z.  angew.  Chem.,  20,  2209  (1907);  abst.,  J. 
Chem.  Soc.,  94,  II,  130  (1908).  M.  Busch  and  G.  Blume,  "  Quantitative  Deter- 
mination of  Picric  Acid,"  Z.  angew.  Chem.,  21,  354  (1908);  abst.,  J.  Chem.  Soc. 
94,  II,  328  (1908).  H.  Franzen  and  E.  Lohmann,  "  The  Use  of  Nitron  in  the 
Determination  of  Nitric  Acid  in  Fluids  Containing  Much  Organic  Matter,"  J. 
prakt.  Chem.,  79,  330  (1909);  abst.}  J.  Chem.  Soc.,  96,  II.  517  (1909).  A.  Hes, 
"Gravimetric  Determination  of  Nitric  Acid,"  Z.  anal.  Chem.,  48,81  (1909); 
abst.,  J.  Chem.  Soc.,  96,  II,  265  (1909).  M.  Busch,  "Reply  to  A.  Hes"  (lee. 
cit.),  Z.  anal.  Chem.,  48,  368  (1909);  abst.,  J.  Chem.  Soc.,  96,  II,  615  (1909). 
P.  Pooth,  "  A  Contribution  to  the  Gravimetric  Determination  of  Nitric  Acid 
ace.  to  M.  Busch  by  Means  of  Nitron,"  Z.  anal.  Chem.,  48,  365  (1909);  abst., 


NITROPHENOL  117 

J.  Chem.  Soc.,  96,  II,  615  (1909).  C.  Paal  and  A.  Ganghofer,  "  The  Determination 
of  Nitric  Acid  with  Nitron,"  Z.  anal.  Chem.,  48,  545  (1909);  abst.,  J.  Chem.  Soc., 
96  II  759  (1909).  C.  Paal  and  A.  Ganghofer,  "  Determination  of  Saltpeter  in 
Meat  with  Nitron,"  Z.  Nahr.  Genussm.,  19,  322  (1910);  abst.,  J.  Chem.  Soc.,  98, 
II,  453  (1910).  L.  Radlberger,  "The  Use  of  M.  Busch's  Nitron  for  the 
Analysis  of  Chili  Saltpeter,"  Oesterr.  Ung.  Z.  Zuckerind.,  39,  433;  abst.,  Chem. 
Zentr.,  (5)  14,  II,  685  (1910);  C.  A.,  5, 1721  (1911). 

NITROPHENOL,   ORTHO- 
C6H4OH  N02.    Mol.  Wt.  139.05 

Sulphur-yellow  needles  or  prisms,  melting  at  44°  to  45°  C.,  easily 
soluble  in  alcohol  and  in  ether,  freely  soluble  in  hot  water,  and  but 
slightly  soluble  in  cold  water. 

NITROPHENOL,  PARA- 

C6H4OH  NO 2.    Mol.  Wt.  139.05 

Colorless  needles  or  monoclinic  prisms,  melting  at  112°  C.  and 
easily  soluble  in  alcohol;  to  some  extent  also  in  water. 

NITROSOBETANAPHTHOL 

Ci0H6(NO)(OH).    Mol.  Wt.  173.07 

Orange-brown  crystals,  melting  at  109°  C.,  insoluble  in  cold  water, 
very  difficultly  soluble  in  boiling  water,  and  very  easily  soluble  in 
ether,  benzene,  and  hot  alcohol.  It  is  used  principally  for  the 
qualitative  separation  of  nickel  and  cobalt. 

PALLADIUM 
Pd.    Atomic  Wt.  106.7 

Palladium  occurs  in  the  form  of  foil  and  wire  which  in  appearance 
greatly  resemble  platinum;  also  in  the  form  of  palladium-sponge,  a 
gray  spongy  mass,  and  as  palladium  black.  The  compact  metal 
is  soluble  in  hot  nitric  and  in  nitrohydrochloric  acids.  Palladium 
sponge  is  soluble  also  in  hydrochloric  acid  in  the  presence  of  air. 

TESTS   OF  PURITY 

Differentiation  Between  Palladium  Foil  and  Platinum  Foil.  —  On  placing  1 
drop  of  an  alcoholic  solution  of  iodine  on  palladium  foil,  and  allowing  it  to 


118  CHEMICAL  REAGENTS 


evaporate  spontaneously  in  the  air,  a  black  spot  will  be  formed  on  the  palladium 
which  will  disappear  on  heating  the  foil  to  redness.  On  platinum  foil  similarly 
treated,  no  spot  is  formed. 

Copper  and  Iron.  —  Dissolve  the  palladium  in  nitrohydrochloric  acid,  and 
evaporate  the  excess  of  acid  on  the  water-bath.  Dissolve  the  residue  in  water, 
and  add  ammonia  water  until  the  flesh-colored  precipitate  of  ammonium  palladous 
chloride  first  formed  redissplves.  Then  pass  into  the  solution  gaseous  hydrochloric 
acid,  whereby  the  palladium  is  precipitated  as  yellow  palladosamine  chloride, 
while  iron  and  copper  remain  in  the  solution.  .  The  precipitate  is  filtered  off, 
and  the  filtrate  treated  with  ammonia  water  in  excess.  No  coloration  or  precipi- 
tation should  ensue.  (Indicating  none  present.) 

NOTE.  —  Regarding  the  quantitative  determination  of  palladium  and  its 
separation  from  other  metals,  see  Fresenius,  Anleitung  zur  quantitativen  chemishen 
Analyse,  6  ed.,  1,  348,  481;  Fresenius-Cohn,  Quantitative  Chemical  Analysis,  1, 
389.  H.  Erdman  and  O.  Makowka,  Ber.,  37,  2694  (1904);  abst.,  J.  Chem.  Soc., 
86,  II,  594  (1904).  Z.  anal.  Chem.,  46,  141,  146  (1907);  abst.,  J.  Chem.  Soc.,  92, 
403  (1907).  A.  Gutbier  and  F.  Falco,  Z.  anal.  Chem.,  48,  555  (1909);  abst., 
J.  Chem.  Soc.,  96,  II,  768  (1909).  Z.  anal.  Chem.,  49,  287,  492  (1910);  abst., 
J.  Chem.  Soc.,  98,  II,  459,  756  (1910). 

PALLADIUM   CHLORIDE 
(Palladous  Chloride) 
PdCl2.    Mpl.  Wt.  177.62 

A  dark-brown  powder,  yielding  a  turbid  solution  in  water  in  con- 
sequence of  the  formation  of  a  basic  salt;  clearly  soluble  on  adding 
hydrochloric  acid.  The  preparation  contains  about  60  per  cent  of 
palladium,  the  theoretical  per  cent  calculated  from  the  formula 

PdCl2  being  60.08. 

TEST   OF  PURITY 

Quantitative  Determination  of  Palladium.  —  Dissolve  0.5  gm.  of  palladium 
chloride  in  2  to  3  c.c.  of  hydrochloric  acid,  dilute  with  100  c.c.  of  water,  and  com- 
pletely precipitate  the  palladium  by  passing  into  the  solution  acetylene  gas. 
Filter  off  the  precipitate,  wash  it  free  from  chlorides .  with  water,  ignite  it,  still 
moist,  in  a  porcelain  crucible,  cautiously  at  first,  then  more  strongly,  finally  in  a 
current  of  hydrogen,  and  weigh. 

PALLADIUM   NITRATE 

(Palladous  Nitrate) 
Pd(NO3)2.    Mol.  Wt.  230.72 

A  brown,  deliquescent  salt,  yielding  a  turbid  solution  with  water, 
due  to  the  almost  invariable  presence  of  some  basic  salt. 

TEST   OF  PURITY 

Quantitative  Determination  of  Palladium.  —  Dissolve  0.5  gm.  of  palladium 
nitrate  in  5  c.c.  of  nitric  acid  and  10  c.c.  of  hydrochloric  acid,  heating  on  the 


PALLADIUM  AND  SODIUM  CHLORIDE  119 


water-bath.  Evaporate  the  solution,  dissolve  the  residue  in  10  c.c.  of  hydro- 
chloric acid,  and  again  evaporate  to  dryness.  Dissolve  the  residue  in  2  to  3 
c.c.  of  hydrochloric  acid,  dilute  with  100  c.c.  of  water,  and  conduct  acetylene 
gas  into  the  solution  until  the  palladium  is  completely  precipitated.  Filter  off 
the  precipitate,  wash  it  with  water  until  free  from  chlorides,  ignite  it,  still  moist, 
in  a  porcelain  crucible,  cautiously  at  first,  then  more  strongly,  finally  in  a  current 
of  hydrogen,  and  weigh. 

PALLADIUM  AND   SODIUM  CHLORIDE 

(Sodium  Fallacious  Chloride) 
PdCl22NaCl+3H2O.     Mol.  Wt.  348.59 
A  reddish-brown  powder,  soluble  in  water. 
TEST  OF  PURITY 

Quantitative  Determination  of  Palladium. — This  test  is  to  be  carried  out 
as  described  under  Palladium  Chloride. 

PHENACETOLIN 

A  brown  dye,  soluble  in  alcohol.  Phenacetolin  is  a  product 
resulting  from  the  action  of  concentrated  sulphuric  acid  on  glacial 
acetic  acid  and  phenol.  The  indicator  solution  is  prepared  by  digest- 
ing 1  gm.  of  phenacetolin  with  warm  alcohol,  then  diluting  to  100 

c.c.,  and  filtering. 

TEST  OF  SENSITIVENESS 

Add  2  drops  of  the  indicator  solution  to  100  c.c.  of  distilled  water.  On  the 
addition  of  0.05  c.c.  of  decinormal  potassium  hydroxide  solution,  the  light-brown 
color  of  the  liquid  should  pass  into  pink;  on  the  further  addition  of  0.05  c.c.  of 
decinormal  hydrochloric  acid,  the  color  should  change  to  a  golden  yellow. 

NOTE.  —  Concerning  the  properties  and  use  of  phenacetolin  as  an  indicator, 
see  Glaser,  Indikatoren  der  Azidimetrie  und  Alkalimetrie,  69.  See  also  Cohn, 
Indicators  and  Test  Papers,  2  ed.,  page  122  (1902). 

PHENOLPHTHALEIN 
C2oH1404.      Mol.  Wt.  318.11 

A  white,  or  yellowish-white,  powder  easily  soluble  in  alcohol,  and 
melting  at  about  260°  C.  Phenolphthalein  is  used  as  an  indicator  in 
the  form  of  a  solution  of  1  gm.  in  100  c.c.  of  neutral  95  per  cent  alcohol. 

TESTS   OF  PURITY 

Non-volatile  Matter.  —  0.5  gm.  of  phenolphthalein  when  ignited  should  yield 
no  weighable  residue.  (Indicating  less  than  0.1  per  cent.) 


120  CHEMICAL  REAGENTS 


Solubility  in  Alcohol.  —  1  gm.  of  phenolphthalein  should  give  a  clear  solution 
with  15  c.c,  of  95  per  cent  alcohol.  The  1  :  100  alcoholic  solution  should  be 
colorless. 

Sensitiveness.  —  To  250  c.c.  of  water,  which  has  been  well  boiled  and  then 
cooled,  add  3  to  5  drops  of  phenolphthalein  solution;  the  solution  should  require 
not  more  than  0.05  c.c.  of  decinormal  potassium  hydroxide  solution  to  produce  a 
coloration. 

Fluorane.  —  0.5  gm.  of  phenolphthalein  should  completely  dissolve  in  a 
mixture  of  1  c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.168)  and  50  c.c.  of  water. 
(Indicating  none  present.) 


PHENYLHYDRAZINE 

C6H5NHNH2.     Mol.  Wt.  108.08 

A  colorless,  or  slightly  yellowish,  highly  refractive  liquid,  boiling  at 
243°  C.,  and  solidifying  when  cold  with  the  formation  of  monoclinic 
plates,  melting  at  19°  C.  Phenylhydrazine  is  but  slightly  soluble 
in  cold  water,  but  is  more  readily  soluble  in  hot  water,  and  is  easily 
soluble  in  alcohol  and  in  ether.  It  is  very  sensitive  to  air. 

TEST  OF  PURITY 

Solubility.  —  2  c.c.  of  phenylhydrazine,  when  shaken  with  20  c.c.  of  5  per 
cent  acetic  acid,  should  afford  a  clear  solution. 


PHLOROGLUCIN 
C6H3(OH)3+2H2O.     Mol.  Wt.  162.08 

A  white,  or  slightly  yellowish,  crystalline  powder,  which  loses 
its  water  of  crystallization  at  100°  C.,  and  which,  on  being  rapidly 
heated,  melts  at  217°  to  219°  C.,  but  which,  when  slowly  heated, 
melts  at  a  much  lower  temperature  (200°  to  209°  C.).*  Phloroglucin 
is  soluble  in  about  95  parts  water,  and  in  10  parts  of  alcohol  (about 
85  per  cent  by  weight.) 

TEST  OF  PURITY 

Diresorcin.  —  Heat  to  boiling  a  solution  of  0.1  gm.  of  phloroglucin  in  10  c.c. 
of  acetic  anhydride,  cool  the  solution",  and  superimpose  it  upon  10  c.c.  of  concen- 
trated sulphuric  acid.  No  violet  zone  should  appear  at  the  contact  planes  of 
the  liquids.  (Indicating  none  present.) 


A.  Baeyer,  Ber.,  19,  2186  (1886);  abst.,  J.  Chem.  Soc.,  50,  1020  (1886). 


PLATINUM  121 

PLATINUM 

Pt.     Atomic  Wt.  195.2 

Platinum  occurs  in  compact  form  as  foil  or  wire,  and  in  a  state  of 
very  fine  subdivision  as  platinum  sponge  and  platinum  black.  Com- 
pact platinum  has  a  silver-white  color;  platinum  sponge  is  a  grayish, 
spongy  mass,  while  platinum  black  is  a  black  powder. 

TESTS   OF  PURITY 

Foreign  Metals.  —  Dissolve  1  gm.  of  the  metal  in  nitrohydrochloric  acid, 
evaporate  the  solution  to  dryness  on  the  water-bath,  and  convert  the  residual 
platinum  chloride  into  platinum  sponge  by  strongly  igniting.  On  now  treating 
the  sponge  with  nitric  acid  and  filtering,  the  filtrate  should  not  leave  more  than 
traces  of  residue  on  being  evaporated.  (Indicating  at  most  a  trace  present.) 

Silver.  —  Dissolve  platinum  in  nitrohydrochloric  acid,  evaporate  the  solution 
to  dryness  on  the  water-bath,  and  dissolve  the  residue  in  water.  No  white 
residue  should  remain.  (Indicating  none  present.) 

NOTE. — Regarding  the  further  testing  of  platinum  for  slight  impurities, 
see  the  paper  by  F.  Mylius  and  P.  Foerster:  The  Preparation  and  Exam- 
ination of  Pure  Platinum,  Ber.,  25,  665  (1892);  dbst.,  J.  Chem.  Soc.,  62,  789 
(1892). 

PLATINUM  CHLORIDE 

(Platinic  Chloride;  Chlorplatinic  Acid) 

H2PtCl6+6H2O.     Mol.  Wt.  518,07 

A  brownish-red,  crystalline,  very  hygroscopic,  saline  mass,  soluble 
in  water,  alcohol,  and  ether,  with  yellow  color.  The  aqueous  solu- 
tion is  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Solubility  in  Absolute  Alcohol.  —  1  gm.  of  platinum  chloride  should  dissolve 
completely  in  10  c.c.  of  absolute  alcohol,  yielding  a  clear  solution.  Platinic 
chloride  should  also  afford  a  clear,  pure  yellow  solution  with  water;  any  red  or 
dark-brown  tinge  would  indicate  the  presence  of  platinous  chloride  or  iridium. 

Metals  Soluble  in  Nitric  Acid.  —  Strongly  ignite  2  gm.  of  platinic  chloride. 
A  residue  of  platinum  sponge  weighing  0.752  gm.  should  be  obtained.  Digest 
this  residue  with  dilute  nitric  acid  (5  c.c.  of  nitric  acid  and  20  c.c.  of  water)  on 
the  water-bath  for  fifteen  minutes,  then  filter,  evaporate  the  filtrate  on  the  water- 
bath,  and  ignite  the  residue  so  obtained.  The  weight  of  the  latter  should  not 
exceed  0.005  gm.  (Indicating  not  more  than  0.25  per  cent.) 

Sulphates.  —  The  solution  of  1  gm.  of  platinic  chloride  in  20  c.c.  of  water 
should  give  no  precipitate  of  barium  sulphate  on  adding  barium  chloride  solution, 
and  setting  aside  three  hours.  (Indicating  less  than  0.0075  per  cent  SO3.) 

Nitrates.  —  On  mixing  2  c.c.  of  the  1  :  10  solution  with  2  c.c.  of  concentrated 
sulphuric  acid,  and  overlaying  this  mixture  with  2  c.c.  of  feTrous  sulphate  solution, 
no  brownish-red  zone  should  develop  at  the  contact  planes  of  the  two  liquids. 
(Indicating  less  than  0,08  per  cent  N2O5.) 


122  CHEMICAL  REAGENTS 


Barium  Salts.  —  The  1  :  20  solution  of  platinic  chloride  should  afford  no  pre- 
cipitate of  barium  sulphate  on  adding  a  few  drops  of  sulphuric  acid,  and  allowing 
to  stand  three  hours.  (Indicating  less  than  0.002  per  cent  Ba.) 

POIRRIER'S  BLUE 
(Poirrer's  Blue  €46,  Indicator) 

The  ammonium  salt  of  triphenylrosanilinetrisulphonic  acid. 
A  dark-blue  powder,  soluble  in  water  and  in  alcohol.    A  solution 
of  0.2  gm.  in  100  c.c.  of  water  is  used  as  an  indicator.* 

TEST  OF  SENSITIVENESS 

To  45  c.c.  of  absolute  alcohol,  contained  in  a  glass-stoppered  flask  of  50  c.c. 
capacity,  add  3  to  5  drops  of  the  above  solution  of  Poirrier's  blue  and  then  by 
drops  decinormal  solution  of  potassium  hydroxide,  shaking  vigorously  after 
each  drop,  until  the  blue  color  has  changed  into  red.  On  now  adding  0.05  c.c. 
of  decinormal  solution  of  hydrochloric  acid,  the  red  color  should  change  to  blue; 
on  further  addition  of  0.05  c.c.  of  decinormal  potassium  hydroxide  solution  the 
red  color  should  return. 

POTASSIUM  ACETATE  SOLUTION 

A  clear,  colorless  liquid,  neutral,  or  at  most  slightly  acid  to 
phenolphthalein;  specific  gravity  1.176  to  1.180.  100  parts  contain 
about  33  parts  of  potassium  acetate. 

TESTS  OF  PURITY 

Chlorides.  —  Dilute  5  c.c.  of  potassium  acetate  solution  with  20  c.c.  of  water, 
and  add  5  c.c.  of  nitric  acid  followed  by  silver  nitrate  solution.  At  most  a  slight 
opalescent  turbidity  should  develop.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Sulphates.  —  Dilute  10  c.c.  of  potassium  acetate  solution  with  10  c.c.  of  water, 
acidify  with  hydrochloric  acid,  and  add  barium  chloride  solution.  No  change 
should  appear.  (Indicating  less  than  0.01  per  cent  SOs.) 

Heavy  Metals.  —  (a)  15  c.c.  of  potassium  acetate  solution  diluted  with  15  c.c. 
of  water  should  not  become  colored  on  the  addition  of  hydrogen  sulphide  water; 
nor  should  a  precipitate  form.  On  now  adding  a  few  drops  of  ammonium  sulphide 
solution,  neither  a  green  or  brown  color  nor  a  precipitate  should  appear.  (Indi- 
cating none  present.) 

(6)  On  diluting  5  c.c.  of  potassium  acetate  solution  with  20  c.c.  of  water  and 
adding  1  c.c.  of  hydrochloric  acid,  the  solution  should  not  acquire  a  red  color 
with  potassium  sulphocyanate  solution.  (Indicating  less  than  0.00015  per  cent  Fe.) 


*  Poirrier's  blue  is  very  sensitive  to  acids  and  consequently  is  very  well 
adapted  to  the  titration  of  salts  of  weak  bases,  for  example,  alkaloidal  salts, 
which  in  alcoholic  solution  react  toward  the  indicator  like  free  acids.  R.  Engel, 
Compt.  rend.,  102,  214,  262  (1886);  abst.,  J.  Soc.  Chem.  Ind.,  5,  392  (1886). 
J.  Messner,  Z.  angew.  Chem.,  16,  469  (1903);  abst.,  J.  Chem.  Soc.,  84,  519  (1903). 
See  also  Z.  anal.  Chem.,  27,  38  (1888). 


POTASSIUM  ANTIMONATE  123 


Calcium.  —  Dilute  10  c.c.  of  potassium  acetate  solution  with  10  c.c.  of  water, 
and  add  ammonium  oxalate  solution.  No  precipitate  of  calcium  oxalate  should 
form  on  standing  three  hours.  (Indicating  less  than  0.002  per  cent  Ca.) 

POTASSIUM  ANTIMONATE 

(Potassium  Acid  Pyroantimonate)* 
K2H2Sb2O7+4H2O.     Mol.  Wt.  504.68 

A  white,  granular,  crystalline  powder,  difficultly  soluble  in  cold 
water,  and  more  readily  soluble  in  boiling  water. 

TESTS  OF  PURITY 

Suitability  as  a  Reagent  for  Sodium,  f — The  aqueous  solution  of  1  gm.  of  potas- 
sium antimonate  in  100  c.c.  of  boiling  water  should  be  neutral  to  litmus  paper. 

On  adding  1  gm.  of  potassium  chloride,  dissolved  in  10  c.c.  of  water,  to  20 
c.c.  of  the  1  :  100  aqueous  solution,  no  precipitate  should  form  within  fifteen 
minutes. 

To  20  c.c.  of  the  1  :  100  aqueous  solution  add  1  gm.  of  ammonium  chloride 
dissolved  in  10  c.c.  of  water  containing  2  or  3  drops  of  ammonia  water.  No 
precipitate  should  form  within  fifteen  minutes.  J 

POTASSIUM  BICARBONATE 
KHCO3.    Mol.  Wt.  ioo.li 

Colorless,  transparent,  rhombic    prisms  or  plates,  soluble  in  4 

parts  of  water. 

TESTS   OF  PURITY 

Sulphates.  —  On  boiling  the  solution  of  3  gm.  of  potassium  bicarbonate  in 
50  c.c.  of  water  and  6  c.c.  of  hydrochloric  acid  for  several  minutes,  and  then 
adding  barium  chloride  solution,  no  precipitate  of  barium  sulphate  should  form 
within  fifteen  hours.  (Indicating  less  than  0.004  per  cent  SO3.) 

Chlorides.  —  Dissolve  3  gm.  of  potassium  bicarbonate  in  50  c.c.  of  water, 
add  10  c.c.  of  nitric  acid  and  some  silver  nitrate  solution.  More  than  a  slight 
opalescence  should  not  develop.  (Indicating  less  than  0.00075  per  cent  Cl.) 

Nitrates.  —  Dissolve  3  gm.  of  potassium  bicarbonate  and  a  granule  of  sodium 
chloride  in  10  c.c. of  16  per  cent  sulphuric  acid;  after  adding  to  the  solution  1  drop 
of  a  1  :  1000  indigo  solution  and  10  c.c.  of  concentrated  sulphuric  acid,  the  blue 
color  should  not  disappear  on  agitation.  (Indicating  less  than  0.0011  per  cent 
N205.) 

*  The  aqueous  solution  of  potassium  antimonate  is  used  as  a  reagent  for 
sodium.  It  is  best  to  prepare  the  solution  just  before  use  by  dissolving  1  gm. 
of  the  salt  in  100  c.c.  of  boiling  water,  and  filtering.  The  solutions  to  be  tested 
for  sodium  should  be  neutral  or  slightly  alkaline. 

t  A  precipitate  occurring  in  making  these  tests  indicates  that  the  preparation 
is  unsuitable  for  use  as  a  reagent  for  sodium. 

J  If  a  solution  of  1  gm.  of  ammonium  chloride  in  10  c.c.  of  water  is  added  to 
20  c.c.  of  the  1  : 100  aqueous  solution,  a  voluminous  flocculent  precipitate  forms 
within  a  few  minutes,  if  the  addition  of  ammonia  water  is  omitted. 


124  CHEMICAL  REAGENTS 


Silicates.  —  Dissolve  5  gm.  of  potassium  bicarbonate  in  20  c.c.  of  water  and 
15  c.c.  of  hydrochloric  acid,  and  evaporate  the  solution  on  the  water-bath  in  a 
platinum  dish.  Dry  the  residue  for  half  an  hour  at  120°  C.,  and  then  dissolve 
it  in  25  c.c.  of  water  with  3  c.c.  of  hydrochloric  acid.  The  solution  should  be 
perfectly  clear.  (Indicating  none  present.) 

Calcium,  Aluminum,  and  Heavy  Metals.  —  Dissolve  5  gm.  of  potassium 
bicarbonate  in  25  c.c.  of  water  and  15  c.c.  of  diluted  acetic  acid.  Add  5  c.c.  of 
ammonia  water  and  heat  for  half  an  hour  on  the  water-bath.  No  flocks  should 
separate.  (Indicating  less  than  0.04  per  cent  Al.)  On  adding  to  the  solution 
some  ammonium  oxalate  solution  and  ammonium  sulphide  solution,  no  change 
should  appear.  (Indicating  less  than  0.001  per  cent  Ca  and  no  heavy  metals 
present.) 

Phosphates.  —  Dissolve  5  gm.  of  potassium  bicarbonate  in  50  c.c.  of  water, 
add  to  the  solution  50  c.c.  of  nitric  acid,  25  c.c.  of  ammonium  molybdate  solution, 
and  heat  at  30°  to  40°  C.  for  'two  hours.  No  yellow  precipitate  should  form. 
(Indicating  less  than  0.004  per  cent  P^Os.) 

Iron.  —  Dissolve  1  gm.  of  potassium  bicarbonate  in  3  c.c.  of  hydrochloric 
acid  and  100  c.c.  of  water,  add  a  drop  of  nitric  acid  and  boil,  then  add  potassium 
sulphocyanate  solution.  No  red  color  should  develop.  (Indicating  less  than 
0.0008  per  cent  Fe.)  _ 

Residue  on  Ignition.  —  100  parts  of  potassium  bicarbonate,  on  ignition, 
should  leave  69  parts  of  residue.  (Indicating  69  per  cent.) 

Quantitative  Determination.  — Titrate  the  solution  of  1  gm.  of  potassium 
bicarbonate  in  50  c.c.  of  water  with  normal  hydrochloric  acid  solution,  using 
methyl  orange  as  indicator. 

1  c.c.  of  normal  HC1  =  0.10011  gm.  of  KHCO3,  log.  00047. 

POTASSIUM  BINIODATE 
KIO3HIO3.     Mol.  Wt.  389.95 

Small,  white  crystals,  clearly  and  completely  soluble  in  20  parts 
of  cold  water. 

The  preparation  contains  100  per  cent  of  KIOsHIOs. 

TESTS  OF  PURITY 

Chlorates.  —  Dissolve  0.2  gm.  of  potassium  biniodate  in  20  c.c.  of  water,  add 
20  c.c.  of  nitric  acid  and  10  c.c.  of  1  :  20  solution  of  silver  nitrate,  and,  after 
shaking  thoroughly,  filter.  On  adding  to  the  filtrate  10  c.c.  of  about  35  per  cent 
formaldehyde  solution  free  from  chlorides,  and  heating  the  mixture  to  boiling, 
neither  a  turbidity  nor  a  precipitate  should  appear.  (Indicating  less  than  0.15 
per  cent  C12O5.) 

Quantitative  Determination.  —  The  quantitative  determination  may  be  carried 
out  either  acidimetrically  or  iodometrically.  The  salt  to  be  used  for  the  quanti- 
tative determination  must  first  be  brought  to  constant  weight  at  98°  C.  in  a  drying- 
oven. 

(a)  For  the  acidimetric  determination  about  3.5  gm.  of  potassium  biniodate 
are  dissolved  in  200  c.c.  of  water.  The  titration  is  made  with  fifth-normal 
solution  of  potassium  hydroxide  in  the  boiling  solution,  using  phenolphthalein 
as  indicator. 

1  c.c.  of  normal  KOH  =  0.07799  gm.  of  KIO3HIO3,  log.  89204. 

(6)  The  iodometric  determination  is  made  as  follows:  Dissolve  0.10  to  0.15 
gm.  of  potassium  biniodate  in  20  c.c.  of  water,  add  3  gm.  of  potassium  iodide 


POTASSIUM  BISULPHATE  125 


and  5  c.c.  of  hydrochloric  acid,  then  dilute  the  liquid  with  100  c.c.  of  water, 
and  titrate  the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3  =  0.00324958  gm.  of  KIO3HIO3,  log.  51182. 

Potassium  biniodate  may  also  be  tested  as  to  the  correctness  of  its  composition 
by  comparing  the  iodine  found  in  (6)  with  the  quantity  of  iodine  liberated  from 
potassium  biniodate  by  potassium  iodide  without  the  addition  of  an  acid. 

As  will  be  seen  from  the  equations  given  below,  when  potassium  biniodate  is 
decomposed  by  potassium  iodide,  without  the  addition  of  an  acid,  it  liberates 
exactly  one-twelfth  of  the  quantity  of  iodine  which  is  liberated  if  the  same  quantity 
of  potassium  biniodate  is  decomposed  by  potassium  iodide  in  the  presence  of 
hydrochloric  or  sulphuric  acid. 

The  determination  of  the  quantity  of  iodine  liberated,  when  the  decomposition 
of  the  biniodate  takes  place  in  the  absence  of  acid,  is  carried  out  as  follows: 
To  the  solution  of  1  gm.  of  potassium  biniodate  in  20  c.c.  of  water,  add  3  gm.  of 
perfectly  neutral  potassium  iodide.  Dilute  with  100  c.c.  of  water,  and  titrate 
the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution.  It  is  necessary 
in  carrying  out  this  determination  to  use  water  perfectly  free  from  carbon  dioxide, 
i.e.,  thoroughly  boiled.  f 

The  iodine  determined  by  this  method,  as  well  as  that  obtained  under  (6)  and, 
of  course,  also  the  number  of  cubic  centimeters  required  in  the  titrations,  provided 
the  same  quantities  of  potassium  biniodate  are  used,  bear  the  ratio  1  :  12. 

This  determination  is  of  special  value  because  the  correct  composition  of  the 
preparation  may  be  controlled  even  without  knowing  the  exact  titer  of  the 
sodium  thiosulphate  solution. 

NOTE.  —  The  course  of  decomposition  of  biniodate  by  potassium  iodide  in 
the  absence  of  acid  may  be  shown  by  the  following  equations: 

1.  5KHI2O6H-5KI  =  10KIO3+5HI; 

2.  KHI2O6+5HI=KIO3+6I+3H2O. 
One  KHI2Oe,  therefore,  liberates  one  I. 

In  the  presence  of  an  acid,  the  reaction  is  as  follows: 
KHI206+10KI-hllHCl  =  llKCl+6H2O+12I. 
Here,  therefore,  one  KHI2O6  liberates  twelve  I. 

POTASSIUM  BISULPHATE 

(Potassium  Acid  Sulphate) 

KHSO4.    Mol.  Wt.  136.18 

Colorless  crystals,  easily  soluble  in  water.  The  aqueous  solution 
is  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Heavy  Metals.  —  The  solution  of  1  'gm.  of  potassium  bisulphate  in  20  c.c.  of 
water  should  not  be  affected  by  hydrogen  sulphide  water.  On  now  adding 
ammonia  water  to  alkalinity,  and  a  few  drops  of  ammonium  sulphide  solution, 
neither  a  precipitate  nor  a  green  or  brown  color  should  appear.  (Indicating  none 
present.) 

Chlorides.  —  The  1  :  20  aqueous  solution  should  not  be  rendered  more  than 
slightly  opalescent  on  the  addition  of  silver  nitrate  solution.  (Indicating  less 
than  0.002  per  cent  Cl.) 

Arsenic.  —  The  mixture  of  1  gm.  of  finely  powdered  potassium  bisulphate 
with  3  c.c.  of  stannpus  chloride  solution  should  not  acquire  a  dark  color  within 
one  hour.  (Indicating  less  than  0.0015  per  cent  As.) 


126  CHEMICAL  REAGENTS. 


Quantitative  Determination. — Dissolve  1  gm.  of  potassium  bisulphate  in 
50  c.c.  of  water,  and  titrate  with  normal  solution  of  potassium  hydroxide,  using 
methyl  orange  as  the  indicator.  ^ 

1  c.c.  of  normal  KOH  =  0.13618  gm.  of  KHSO4,  log.  13411. 


POTASSIUM  BISULPHITE,  Meta 
K2S2O6.     Mol.  Wt.  222.34 

A  white,  crystalline  powder,  having  an  odor  of  sulphurous  acid 
and  easily  soluble  in  water.  The  aqueous  solution  is  acid  to  litmus 

paper. 

TESTS   OF  PURITY 

Chlorides.  —  Dissolve  1  gm.  of  potassium  bisulphite  in  10  c.c.  of  water, 
add  10  c.c.  of  perhydrol,  make  alkaline  with  a  solution  of  potassium  hydroxide 
purest,  and  evaporate  on  the  water-bath.  Dissolve  the  residue  in  20  c.c.  of 
water,  acidulate  with  nitric  acid,  and  add  silver  nitrate  solution.  At  most  a 
slight  opalescence  should  appear.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  Dissolve  2  gm.  of  potassium  bisulphite  in  10  c.c.  of  water 
and  20  c.c.  of  hydrochloric  acid,  evaporate  on  the  water-bath,  dissolve  the  residue 
in  20  c.c.  of  water,  and  add  to  the  solution  hydrogen  sulphide  water.  No  change 
should  appear,  nor  should  a  precipitate  form  on  adding  ammonia  water  and 
ammonium  sulphide  solution.  (Indicating  none  present.) 

Arsenic.  —  Introduce  5  gm.  of  potassium  bisulphite,  a  little  at  a  time,  into 
25  c.c.  of  nitric  acid  (sp.gr.  1.3),  add  5  c.c.  of  concentrated  sulphuric  acid,  and 
evaporate  the  mixture,  first  as  far  as  possible  on  the  water-bath  and  then  upon 
the  sand-bath,  until  sulphuric  acid  vapors  begin  to  be  evolved.  Cool  the  residue 
and  dissolve  it  in  50  c.c.  of  water.  Set  in  operation  a  Marsh  apparatus  by  means 
of  20  gm.  of  arsenic-free  zinc  and  diluted  (1  :  5)  sulphuric  acid,  and  add  the  solu- 
tion in  small  portions  to  the  generating  flask  of  the  apparatus.  After  one  hour 
no  deposit  of  arsenic  should  be  visible  in  the  reduction-tube.  (Indicating  less 
than  0.0002  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  bisulphite  in 
boiled  water  and  dilute  to  100  c.c.  Allow  the  solution  to  run  from  a  burette 
into  a  mixture  of  30  c.c.  of  decinormal  iodine  solution  and  5  c.c.  of  hydrochloric 
acid,  with  constant  shaking,  until  decolorization  is  complete. 

1  c.c.  of  decinormal  1  =  0.0055585  gm.  of  K^Os,  log.  74496. 


POTASSIUM  BITARTRATE- 
(Potassium  Acid  Tartrate) 
KHC4H4O6.    Mol.  Wt.  188.14 

A  white,  crystalline  powder,  soluble  in  about  200  parts  of  cold, 
and  in  20  parts  of  boiling,  water,  and  insoluble  in  alcohol.  Potassium 
bitartrate  is  also  soluble  in  a  solution  of  sodium  hydroxide,  and  in 
potassium  carbonate  solution  with  the  evolution  of  carbon  dioxide. 
The  preparation  contains  100  per  cent  of 


POTASSIUM  BROMATE  127 


TESTS   OF  PURITY 

Moisture.  —  5  gm.  of  potassium  bitartrate,  when  dried  at  100°  C.,  should  not 
suffer  any  loss  in  weight.  (Indicating  none  present.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  bitartrate  hi  20  c.c.  of  water  and 
add  5  c.c.  of  nitric  acid.  The  solution  must  not  be  rendered  more  than  slightly 
opalescent  on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than 
0.002  per  cent  Cl.) 

Sulphates.  —  Dissolve  1  gm.  of  potassium  bitartrate  in  20  c.c.  of  water,  add 
5  c.c.  of  nitric  acid  and  barium  nitrate  solution.  No  precipitate  should  form 
within  fifteen  hours.  (Indicating  less  than  0.035  per  cent  SOs.) 

Ammonium  Compounds.  —  On  heating  2  gm.  of  potassium  bitartrate  with  10 
c.c.  of  sodium  hydroxide  solution  no  vapors  of  ammonia  should  be  evolved  (to 
be  ascertained  by  moist  litmus  paper).  (Indicating  less  than  0.00175  per  cent 
NH3.) 

Calcium.  —  Dissolve  1  gm.  of  potassium  bitartrate  in  5  c.c.  of  diluted  acetic 
acid  and  25  c.c.  of  water,  with  the  aid  of  heat.  Allow  to  become  perfectly  cold, 
filter,  and  to  the  filtrate  add  a  few  drops  of  ammonium  oxalate  solution.  The 
liquid  should  show  no  turbidity  within  ten  minutes.  (Indicating  less  than 
0.025  per  cent  Ca.) 

Heavy  Metals.*  —  The  solution  of  5  gm.  of  potassium  bitartrate  in  25  c.c. 
of  water  and  25  c.c.  of  ammonia  water  should  show  no  change  on  the  addition 
of  hydrogen  sulphide  water.  (Indicating  none  present.) 

Quantitative  Determination.  —  (a)  Dissolve  5  gm.  of  potassium  bitartrate  in 
250  c.c.  of  hot  water,  and  while  boiling  titrate  the  solution  with  normal  soluti6n 
of  potassium  hydroxide,  using  phenolphthaHn  as  the  indicator. 

1  c.c.  of  normal  KOH  =  0.18814  gm.  of  KHC4H4O6,  log.  27448. 

(6)  Cautiously  incinerate  3  gm.  of  potassium  bitartrate  in  a  platinum  crucible. 
When  cold,  dissolve  the  contents  of  the  crucible  in  water,  and  titrate  with  normal 
hydrochloric  acid  solution,  using  methyl  orange  as  the  indicator. 

1  c.c.  of  normal  HC1  =  0.18814  gm.  of  KHC4H4O6,  log.  27448, 


POTASSIUM  BROMATE 
KBrO3.     Mol.  Wt.  167.02 

White  crystals  or  crystalline  powder,  soluble  in  15  parts  of  cold, 
or  2  parts  of  boiling,  water.  The  aqueous  solution  is  neutral  to 
litmus  paper.  The  preparation  contains  100  per  cent  of  KBrOa. 

TESTS   OF  PURITY 

Potassium  Bromide.  —  Dissolve  2  gm.  of  potassium  bromate  in  30  c.c.  of 
water  and  add  diluted  sulphuric  acid.  The  solution  should  not  immediately 
acquire  a  yellow  color.  (Indicating  less  than  0.04  per  cent  KBr.) 

Quantitative  Determination.  —  For  this  purpose,  the  salt  must  be  dried  over 
sulphuric  acid.  Dissolve  0.10  to  0.15  gm.  of  the  dried  potassium  bromate  in 
20  c.c.  of  water,  add  3  gm.  of  potassium  iodide  and  5  c.c.  of  hydrochloric  acid, 
and  titrate  the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3  =  0.00278366  gm.  of  KBrO3,  log.  44461. 


*  Regarding  the  examination  of  potassium  bitartrate  for  lead,  see  Tatlock 
and  Thompson,  Analyst,  33,  173  (1908);  dbst.,  C.  A.,  2,  2269  (1908). 


I 

128  CHEMICAL  REAGENTS 


POTASSIUM  BROMIDE 

KBr.     Mol.  Wt.  119.02 

White,  cubical,  lustrous  crystals,  permanent  in  the  air;  soluble 
in  2  parts  of  water  and  in  about  200  parts  of  85  per  cent  alcohol. 

TESTS  OF  PURITY 

Potassium  Carbonate.  —  Powdered  potassium  bromide  should  not  immedi- 
ately render  red  litmus  paper  blue,  and  the  1  :  20  aqueous  solution  should 
not  be  reddened  on  the  addition  of  phenolphthalein  solution.  (Indicating  less 
than  0.04  per  cent  K2CO3.) 

Potassium  Bromate.  —  The  1  :  10  aqueous  solution  of  potassium  bromide 
should  not  become  colored  on  the  addition  of  diluted  sulphuric  acid;  chloroform 
shaken  with  this  mixture  should  not  become  yellow.  (Indicating  less  than  0.004 
per  cent  KBrO3.) 

Heavy  Metals,  Sulphates,  and  Barium  Salts.  —  20  c.c.  portions  of  the  1  :  20 
solution  should  show  no  change  with  hydrogen  sulphide  water  (indicating  no 
heavy  metals  present),  or  with  barium  nitrate  solution  (indicating  less  than 
0.00125  per  cent  SO3),  or  with  diluted  sulphuric  acid.  (Indicating  less  than  0.002 
per  cent  Ba.) 

Iodides.  —  Add  3  drops  of  ferric  chloride  solution  and  some  starch  solution 
to  the  1  :  20  aqueous  solution  of  potassium  bromide.  No  blue  coloration  should 
take  place  within  ten  minutes.  (Indicating  less  than  0.1  per  cent  I.) 

Quantitative  Determination  and  Test  for  Excess  of  Potassium  Chloride.*  — 
On  adding  a  few  drops  of  potassium  chromate  solution  to  50  c.c.  of  the  aqueous 
solution,  prepared  from  3  gm.  of  potassium  bromide,  dried  at  100°  C.  before 
weighing,  dissolved,  and  diluted  with  water  to  500  c.c.,  the  solution  should  require 
not  more  than  25.4  c.c.  and  not  less  than  25.1  c.c.  of  decinormal  silver  nitrate 
solution  to  produce  a  permanent  red  color.  (Indicating  not  more  than  1.3  per 
cent  KC1.) 

1  c.c.  of  decinormal  AgNO3  =  0.011902  gm.  KBr,  log.  07562. 

POTASSIUM   CARBONATE 
K2CO3.     Mol.  Wt.  138.3 

A  white,  granular,  hygroscopic  powder  of  alkaline  reaction, 
soluble  in  1  part  of  water,  but  insoluble  in  absolute  alcohol.  The 
preparation  should  contain  at  least  99  per  cent  of  K2C03. 

TESTS   OF  PURITY 

Heavy  Metals.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should  show  no  change 
of  color  on  the  addition  of  hydrogen  sulphide  water.  Nor  should  any  change 
of  color  be  shown  upon  acidulating  20  c.c.  of  the  1  :  20  solution  with  acetic  acid 
and  then  adding  hydrogen  sulphide  water.  (Indicating  none  present.) 

Chlorides.  —  The  solution  of  1  gm.  of  potassium  carbonate  in  20  c.c.  of  water, 


*  Potassium  chloride  is  almost  always  present  in  potassium  bromide,  though 
usually  in  very  small  quantities  only. 


POTASSIUM  CARBONATE  SOLUTION  129 


acidified  with  nitric  acid,  should  afford  at  most  a  slight  opalescence  on  the 
addition  of  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Sulphates.  —  On  acidifying  20  c.c.  of  the  1  :  20  aqueous  solution  with  hydro- 
chloric acid,  then  boiling  for  a  few  minutes  and  adding  barium  chloride  solution, 
no  precipitate  of  barium  sulphate  should  form  within  fifteen  hours.  (Indicating 
less  than  0.0075  per  cent  SO3.) 

Nitrates.  —  Dissolve  0.2  gm.  of  potassium  carbonate  in  2  c.c.  of  diluted  sul- 
phuric acid,  and  mix  the  fluid  with  2  c.c.  of  concentrated  sulphuric  acid.  On 
now  cooling  the  solution,  and  overlaying  it  with  1  c.c.  of  a  ferrous  sulphate  solution, 
no  colored  zone  should  form  at  the  contact-surfaces  of  the  two  liquids.  (Indi- 
cating less  than  0.08  per  cent  N2O5.) 

Potassium  Cyanide.  —  Dissolve  0.5  gm.  of  ferrous  sulphate  in  5  c.c.  of  water, 
add  5  c,c.  of  a  1  :  20  potassium  carbonate  solution,  and  1  or  2  drops  of  ferric 
chloride  solution.  Heat  to  about  60  to  70°  C.,  and  acidulate  with  hydrochloric 
acid.  No  green  color  should  develop,  nor  should  a  blue  precipitate  form.  (Indi- 
cating less  than  0.048  per  cent  CN.) 

Sulphides,  Sulphites,  and  Thiosulphates.  —  On  pouring  1  c.c.  of  the  1  :  20 
aqueous  solution  into  10  c.c.  of  decinormal  silver  nitrate  solution,  a  yellowish- 
white  precipitate  forms,  which  should  not  become  darker  (gray  to  brownish  to 
black)  on  being  heated  to  60°  to  70°  C.  (Indicating  less  than  0.02  per  cent  S, 
0.008  per  cent  SO2,  or  0.08  per  cent  K2S2O3.) 

Phosphates.  —  Dissolve  5  gm.  of  potassium  carbonate  in  50  c.c.  of  water, 
acidulate  the  solution  with  50  c.c.  of  nitric  acid,  and  add  25  c.c.  of  ammonium 
molybdate  solution.  No  yellow  precipitate  should  form  on  standing  two  hours 
at  about  40°  C.  (Indicating  less  than  0.004  per  cent  P2Os.) 

Silicates.  —  Dissolve  5  gm.  of  potassium  carbonate  in  a  platinum  dish  in 
20  c.c.  of  hydrochloric  acid  and  20  c.c.  of  water,  and  evaporate  to  dryness.  Dry 
the  residue  for  half  an  hour  at  about  120°  C.,  and  then  dissolve  it  in  3  c.c.  of 
hydrochloric  acid  and  25  c.c.  of  water.  The  solution  must  be  perfectly  clear. 
(Indicating  none  present.) 

Aluminum  and  Calcium.  —  Dissolve  5  gm.  of  the  carbonate  in  25  c.c.  of  water 
and  25  c.c.  of  acetic  acid  (sp.gr.  1.041),  add  12  c.c.  of  ammonia  water,  and  heat 
for  half  an  hour  on  the  water-bath.  No  flocculent  precipitate  should  form, 
(indicating  less  than  0.04  per  cent  Al),  nor  should  any  change  take  place  on  the 
addition  of  ammonium  oxalate  solution.  (Indicating  less  than  0.001  per  cent  Ca.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  carbonate  in 
50  c.c.  of  water,  and  titrate  with  normal  solution  of  hydrochloric  acid,  using 
methyl  orange  as  indicator.  At  least  14.3  c.c.  of  the  hydrochloric  acid  solution 
should  be  required  to  produce  the  red  end-point. 

1  c.c.  of  normal  HC1  =  0.0691  gm.  of  K2C03,  log.  83948. 

POTASSIUM   CARBONATE   SOLUTION 

A  clear,  colorless,  alkaline  liquid,  of  specific  gravity  1.334  to 
1.338.     100  parts  contain  about  33  parts  of  potassium  carbonate. 
TESTS  OF  PURITY 

The  tests  to  be  made  are  those  given  under  Potassium  Carbonate.  But  use 
3  c.c.  of  potassium  carbonate  solution  for  each  gram  of  potassium  carbonate. 

Quantitative  Determination.  —  Dilute  5  gm.  of  potassium  carbonate  solution 
with  30  c.c.  of  water  and  titrate  with  normal  solution  of  hydrochloric  acid,  using 
methyl  orange  as  indicator.  At  least  23.7  c.c.  of  the  acid  solution  should  be 
required  to  effect  the  color  change. 

1  c.c.  of  normal  HC1  =0.0691  gm.  of  K2CO3,  log.  83948. 


130  CHEMICAL  REAGENTS 

POTASSIUM  CHLORATE 

KC1O3.     Mol.  Wt.  122.56 

Colorless,  lustrous,  tabular,  crystals  soluble  in  17  parts  of  cold, 
and  in  2  parts  of  boiling,  water,  and  in  130  parts  of  about  85  per 
cent  (by  weight)  alcohol.  The  salt  is  practically  insoluble  in  absolute 
alcohol  and  in  ether.  The  aqueous  solution  is  neutral. 

TESTS   OF  PURITY 

Chlorides.  — •  20  c.c.  of  the  1  :  20  aqueous  solution  should  not  be  affected  by 
silver  nitrate  solution.  (Indicating  less  than  0.001  per  cent  Cl.) 

Heavy  Metals.  —  The  solution  of  3  gm.  of  potassium  chlorate  in  30  c.c  .  of 
warm  water  should  be  perfectly  clear,  and  should  remain  unchanged  on  the  addi- 
tion of  hydrogen  sulphide  water.  (Indicating  none  present.) 

Calcium.  —  The  solution  of  1  gm.  of  potassium  chlorate  in  20  c.c.  of  water 
should  show  no  change  on  adding  ammonium  oxalate  solution.  (Indicating  less 
than  0.005  per  cent  Ca.) 

Bromates.  —  Gently  ignite  1  gm.  of  potassium  chlorate,  dissolve  the  residue 
in  water,  and  add  to  the  solution  a  few  drops  of  chlorine  water.  On  shaking  this 
mixture  with  chloroform,  the  latter  should  not  become  colored  yellow  or  brown. 
(Indicating  less  than  0.08  per  cent  Br2O5.) 

Nitrates.  —  On  heating  1  gm.  of  potassium  chlorate  with  5  c.c.  of  sodium 
hydroxide  solution  (sp.gr.  1.3),  and  a  mixture  of  0.5  gm.  of  zinc  dust  and  0.5  gm. 
of  powdered  iron,  no  ammonia  should  be  evolved  (to  be  ascertained  by  moist 
litmus  paper).  (Indicating  less  than  0.0016  per  cent  ^Oe.) 

Sulphates.  —  On  adding  barium  chloride  solution  to  20  c.c.  of  the  1  :  20 
aqueous  solution,  no  precipitate  of  barium  sulphate  should  form  on  standing 
fifteen  hours.  (Indicating  less  than  0.001  per  cent  SOs.) 

Arsenic.  —  Pour  150  c.c.  of  hydrochloric  acid  over  20  gm.  of  potassium 
chlorate  in  a  porcelain  dish.  As  soon  as  the  evolution  of  chlorine  has  slackened, 
heat  the  solution  on  the  water-bath  until  free  from  the  odor  of  chlorine.  A 
Marsh  apparatus  is  set  in  operation,  containing  20  gm.  of  arsenic-free,  granulated 
zinc  and  dilute  (1:5)  sulphuric  acid.  The  solution  obtained  above,  cooled  and 
diluted  with  water,  is  then  introduced  into  the  generating  flask  of  the  apparatus 
in  small  portions  at  a  time.  No  deposit  of  arsenic  should  be  visible  in  the  reduc- 
tion tube  within  one  hour.  (Indicating  less  than  0.00005  per  cent  As.) 

Quantitative  Determination.*  —  Into  a  glass-stoppered  flask  of  400  to  500 
c.c.  capacity  introduce  50  c.c.  of  hydrochloric  acid,  replace  the  air  in  the  flask  by 
carbon  dioxide,  add  a  solution  of  5  gm.  of  potassium  iodide  in  10  c.c.  of  boiled  and 
cooled  water,  add  10  c.c.  of  a  solution  of  1  gm.  of  the  potassium  chlorate  in  100 
c.c.  of  water.  Close  the  flask,  let  the  mixture  stand  one  hour  in  a  dark  place, 
dilute  it  with  200  c.c.  of  boiled  and  cooled  water  and  then  titrate  with  decinormal 
sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Naa&Os  =  0.00204266  gm.  of  KC103,  log,  31019. 


*  A.  Kolb  and  E.  Davidson,  Z.  angew.  Chem.,  17, 1883  (1904);  abst.,  J.  Chem. 
Soc.,  88,  II,  59  (1904). 


POTASSIUM  CHLORIDE  131 

POTASSIUM   CHLORIDE 

KC1.    Mol.  Wt.  74.56 

Colorless,  cubical  crystals,  or  white,  crystalline  powder,  soluble 
in  3  parts  of  cold  water;  insoluble  in  absolute  alcohol  or  ether. 
The  aqueous  solution  is  neutral. 

TESTS   OF  PURITY 

Heavy  Metals  and  Alkaline  Earths.  —  The  solution  of  3  gm.  of  potassium 
chloride  in  50  c.c.  of  water  should  not  be  affected  by  ammonium  oxalate  solution; 
or  by  sodium  carbonate  solution ;  or  by  ammonium  sulphide  solution.  (Indicating 
no  heavy  metals  present,  and  less  than  0.01  per  cent  earths  as  Ca.) 

Sulphates.  —  On  adding  barium  chloride  solution  to  20  c.c.  of  the  1  :  20 
aqueous  solution,  no  precipitate  of  barium  sulphate  should  form  on  standing 
fifteen  hours.  (Indicating  less  than  0.001  per  cent  SO3.) 

Nitrates.  —  Dissolve  1  gm.  of  potassium  chloride  in  10  c.c.  of  water  and  add 
1  drop  of  1  :  1000  indigo  solution  and  10  c.c.  of  concentrated  sulphuric  acid; 
on  shaking,  the  blue  color  of  the  mixture  should  not  disappear.  (Indicating 
less  than  0.0032  per  cent  N2O5.) 

Chlorates.  —  20  c.c.  of  the  1  :  20  solution  of  potassium  chloride  should  not  be 
colored  blue  on  the  addition  of  zinc  iodide-starch  solution  and  hydrochloric 
acid.  (Indicating  less  than  0.018  per  cent  C12O5.) 

Magnesium.  —  Dissolve  1  gm.  of  potassium  chloride  in  5  c.c.  of  water  and 
add  5  c.c.  of  ammonia  water  and  some  ammonium  phosphate  solution.  No 
precipitate  should  form  on  standing  fifteen  hours.  (Indicating  less  than  0.002 
per  cent  Mg.) 

POTASSIUM   CHROMATE 

(Yellow  Potassium  Chromate) 

K2CrO4.     Mol.  Wt.  194.2 

Yellow,  rhombic  crystals,  permanent  in  the  air,  soluble  in  2 
parts  of  cold  water.  The  1  :  20  aqueous  solution  is  slightly  alkaline 
to  litmus  paper. 

TESTS   OF  [PURITY 

Free  Alkali.  —  The  solution  of  0.1  gm.  of  potassium  chromate  in  25  c.c.  of 
water  should  not  acquire  a  red  color  on  the  addition  of  a  few  drops  of  phenol- 
phthalein  solution.  (Indicating  less  than  0.2  per  cent  as  KOH.) 

Sulphates.  —  Dissolve  3  gm.  of  potassium  chromate  in  100  c.c.  of  water 
and  add  30  c.c.  of  hydrochloric  acid,  followed  by  barium  chloride  solution.  No 
precipitate  of  barium  sulphate  should  form  within  fifteen  hours.  (Indicating  less 
than  0.029  per  cent  SO3.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  chromate  in  20  c.c.  of  water,  add 
to  the  solution  10  c.c.  of  nitric  acid,  and  heat  the  mixture  to  about  50°  C.  On 
now  adding  a  few  drops  of  silver  nitrate  solution,  no  turbidity  or  precipitate 
should  form  within  five  minutes.  (Indicating  less  than  0.0025  per  cent  Cl.) 

Alumina  and  Alkaline  Earths.  —  Dissolve  2  gm.  of  potassium  chromate  in 
30  c.c.  of  water,  add  5  c.c.  of  ammonia  water  and  some  ammonium  oxalate 


132  CHEMICAL  REAGENTS 


solution.  No  precipitate  should  form  within  fifteen  hours.  (Indicating  less 
than  0.1  per  cent  Al  and  less  than  0.005  per  cent  earths  as  Ca.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  chromate  in 
water  and  dilute  to  100  c.c.  Introduce  10  c.c.  of  this  solution  into  a  glass- 
stoppered  flask  of  about  400  c.c.  capacity,  add  2  gm.  of  potassium  iodide,  5  c.c. 
of  16  per  cent  sulphuric  acid,  and  350  c.c.  of  thoroughly  boiled  water.  Titrate 
the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution,  using  starch 
solution  as  the  indicator. 

1  c.c.  of  decinormal  Na2S2O3=  0.0064733  gm.  of  K2Cr04,  log.  81113. 


POTASSIUM   CYANIDE 

KCN.     Mol.  Wt.  65.11 

A  white  powder,  easily  soluble  in  2  parts  of  water,  difficultly 
soluble  in  absolute  alcohol,  but  readily  in  boiling  60  per  cent  alcohol. 
The  aqueous  solution  is  alkaline  to  litmus  paper.  The  salt  contains 
at  least  96  per  cent  of  KCN. 

TESTS  OF  PURITY 

Sulphides.  —  On  adding  a  solution  of  lead  acetate  to  the  solution  of  1  gm.  of 
potassium  cyanide  in  20  c.c.  of  water,  the  resulting  precipitate  should  have  a 
pure  white  color.  (Indicating  less  than  0.003  per  cent  S.) 

Carbonates,  Sulphocyanates,  and  Ferrocyanides.  —  On  adding  5  c.c.  of  hydro- 
chloric acid  to  the  solution  of  1  gm.  of  potassium  cyanide  in  20  c.c.  of  water — 
which  should  be  done  under  anoodwith  n,  good  draft — only  a  slight  efferves- 
cence should  be  perceptible.  (Indicating  about  4  per  cent  CO2.)  On  adding  a 
drop  of  ferric  chloride  solution  to  the  acid  liquid,  neither  a  red  nor  a  blue  color 
should  develop.  (Indicating  less  than  0.015  per  cent  CNS,  or  0.005  per  cent 
Fe[CN]6.) 

Sulphates.  —  On  adding  to  20  c.c.  of  the  1  :  20  aqueous  solution  5  c.c.  of 
hydrochloric  acid,  and  some  barium  chloride  solution,  no  turbidity  should  develop. 
(Indicating  less  than  0.0875  per  cent  SO3.) 

Chlorides.  —  Dissolve  0.5  gm.  of  potassium  cyanide  in  20  c.c.  of  water  and 
add  30  c.c.  of  1  :  20  silver  nitrate  solution  and  10  c.c.  of  nitric  acid.  Filter  off 
the  precipitate,  wash  it  with  water,  dry  it  at  100°  C.,  remove  it  from  the  filter 
and  ignite  it  in  a  porcelain  crucible.  Add  to  the  residue  a  few  pieces  of  zinc 
and  20  c.c.  of  16  per  cent  sulphuric  acid,  let  the  mixture  stand  two  to  three  hours, 
shaking  frequently,  and  filter.  On  adding  to  the  filtrate  nitric  acid  and  silver 
nitrate  solution,  not  more  than  a  slight  opalescence  should  develop.  (Indicating 
less  than  0.004  per  cent  Cl.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  .cyanide  in  water 
and  dilute  to  100  c.c.  Dilute  10  c.c.  of  this  solution  with  90  c.c.  of  water,  add  a 
granule  of  sodium  chloride,  and  titrate  with  decinormal  silver  nitrate  solution 
until  a  permanent,  whitish  turbidity  appears. 

1  C.G.  of  decinormal  AgNOa= 0.013022  gm.  of  KCN,  log.  11467, 


POTASSIUM  BICHROMATE  133 

v 

POTASSIUM  DICHROMATE 

(Potassium  Bichromate) 
K2Cr2O7.    Mol.  Wt.  294.2 

Dark,  yellowish-red,  triclinic  prisms  or  plates,  soluble  in  10  parts 
of  cold,  or  in  about  1.5  parts  of  boiling,  water.  The  aqueous  solution 
reddens  blue  litmus  paper. 

TESTS  OF  PURITY 

Sulphates.  —  Dissolve  3  gm.  of  potassium  dichromate  in  100  c.c.  of  water, 
and  add  30  c.c.  of  hydrochloric  acid  followed  by  barium  chloride  solution.  No 
precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indi- 
cating less  than  0.029  per  cent  SO3.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  dichromate  in  20  c.c.  of  water, 
add  10  c.c.  of  nitric  acid,  and  heat  the  mixture  to  about  50°  C.  On  now  adding 
a  few  drops  of  silver  nitrate  solution,  no  turbidity  should  develop  within  five 
minutes.  (Indicating  less  than  0.0025  per  cent  Cl.) 

Alumina  and  Alkaline  Earths.  —  Dissolve  2  gm.  of  potassium  dichromate 
in  30  c.c.  of  water,  make  alkaline  with  10  c.c.  of  ammonia  water,  and  add 
ammonium  oxalate  solution.  No  precipitate  should  form  within  fifteen  hours. 
(Indicating  less  than  0.1  per  cent  At,  and  less  than  0.005  per  cent  earths  as  Ca.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  dichromate  in 
water,  dilute  to  100  c.c.,  and  introduce  10  c.c.  of  this  solution  into  a  glass-stoppered 
flask  of  about  400  c.c.  capacity,  together  with  2  gm.  of  potassium  iodide  and  5 
c.c.  of  16  per  cent  sulphuric  acid.  Dilute  with  350  c.c.  of  thoroughly  boiled  water, 
and  titrate  the  liberated  iodine  with  decinormal  sodium  thiosulphate  solution, 
using  starch  solution  as  the  indicator. 

1  c.c.  of  decinormal  Na2S2O3  =  0.0049033  gm.  of  K2Cr207,  log.  69049. 

POTASSIUM  FERRICYANIDE 

(Red  Prussiate  of  Potash) 

K3Fe(CN)6.     Mol.  Wt.  329.2 

Ruby-red,  shining  crystals,  soluble  in  2.5  parts  of  cold,  and  in 
1.5  parts  of  boiling,  water.  The  1  :  20  aqueous  solution  is  neutral. 

TESTS   OF  PURITY 

Ferrous  Salts.  —  Dissolve  2  gm.  of  potassium  ferricyanide  in  400  c.c.  of  water 
and  5  c.c.  of  16  per  cent  sulphuric  acid,  and  titrate  the  solution  with  decinormal 
solution  of  potassium  permanganate;  at  most  0.2  c.c.  of  the  permanganate 
solution  should  be  necessary  to  effect  a  color  change  from  yellowish-green  to 
yellowish-red.  In  order  better  to  observe  the  color  change,  compare  the  color 
of  the  solution  that  has  been  titrated  with  that  of  another  solution  of  2  gm. 
of  the  ferricyanide  in  400  c.c.  of  water  and  5  c.c.  of  16  per  cent  sulphuric  acid. 
(Indicating  not  more  than  0.056  per  cent  Fe".) 


134  CHEMICAL  REAGENTS 


Sulphates.  —  On  adding  1  c.c.  of  hydrochloric  acid  to  20  c.c.  of  the  1  :  20 
aqueous  solution,  and  then  adding  barium  chloride  solution,  no  precipitate  of 
barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating  less  than 
0.005  per  cent  SO3.) 

Chlorides.  —  Deflagrate  a  mixture  of  0.5  gm.  of  powdered  potassium  ferri- 
cyanide  and  1  gm.  of  potassium  nitrate*  by  introducing  small  quantities  at  a 
time  into  a  porcelain  crucible  heated  to  redness.  Ignite  for  a  few  minutes  and 
leach  the  melt  with  20  c.c.  of  water.  Filter,  to  the  nitrate  add  0.5  gm.  of  potas- 
sium nitrate,  evaporate  to  dryness,  re-fuse  in  a  porcelain  crucible  until  quiescent, 
and  allow  to  cool.  When  cold,  dissolve  in  20  c.c.  of  water,  add  3  c.c.  of  nitric 
acid  and  silver  nitrate  solution.  The  liquid  should  show  at  most  an  opalescence. 
(Indicating  less  than  0.01  per  cent  Cl.) 

Quantitative  Determination.  —  Dissolve  0.7  gm.  of  potassium  ferricyanide 
in  50  c.c.  of  water,  add  3  gm.  of  potassium  iodide  and  1.5  gm.  of  zinc  sulphate, 
free  from  iron,  shake  thoroughly,  and  titrate  the  free  iodine  with  deeinormal 
sodium  thiosulphate  solution,  using  starch  solution  as  indicator. 

1  c.c.  of  decinormal  Na2S2O3  =  0.03292  gm.  of  K3Fe(CN)6,  log.  51746. 


POTASSIUM  FERROCYANIDE 

(Yellow  Prussiate  of  Potash) 
K4Fe(CN)6+3H20.     Mol.  Wt.  422.35 

Citron-yellow,  tabular  crystals,  which  are  quite  permanent  in 
the  air  and  are  soluble  in  4  parts  of  cold,  and  2  parts  of  boiling, 
water;  insoluble  in  alcohol.  The  1  :  20  aqueous  solution  is  neutral. 

TESTS  OF  PURITY 

Carbonates.  —  On  treating  1  gm.  of  powdered  potassium  ferrocyanide  with 
dilute  sulphuric  acid,  there  should  be  no  evolution  of  gas.  (Indicating  less  than 
0.75  per  cent  CO2.) 

Sulphates.  —  Dissolve  1  gm.  of  potassium  ferrocyanide  in  20  c.c.  of  water, 
and  add  1  c.c.  of  hydrochloric  acid  followed  by  barium  chloride  solution.  The 
solution  should  not  be  affected.  (Indicating  less  than  0.0075  per  cent  SO3.) 

Chlorides.  —  Deflagrate  a  mixture  of  0.5  gm.  of  powdered  potassium  ferro- 
cyanide and  1  gm.  of  potassium  nitrate,*  by  introducing  small  quantities  at  a 
time  into  a  porcelain  crucible  heated  to  redness.  Treat  the  residue  with  20  c.c. 
of  water,  filter,  to  the  filtrate  add  0.5  gm.  of  potassium  nitrate,  and  evaporate 
to  dryness  in  a  porcelain  crucible.  Fuse  the  residue  until  quiescent,  allow  to 
cool,  dissolve  the  melt  in  20  c.c.  of  water,  and  add  3  c.c.  of  nitric  acid  and  silver 
nitrate  solution.  The  liquid  should  not  develop  more  than  an  opalescence. 
(Indicating  less  than  0.01  per  cent  Cl.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  ferrocyanide  in  200 
c.c.  of  water,  add  10  c.c.  of  concentrated  sulphuric  acid,  and  titrate  with  deci- 
normal potassium  permanganate  solution  until  the  color  changes  from  yellowish- 
green  to  yellowish -red. 

1  c.c.  of  decinormal  KMnO4  =  0.042235  gm.  of  K4Fe(CN)6+3H2O,  log.  62567. 


*  The  potassium  nitrate  should  be  tested  for  chloride  and  perchlorate.    See 
under  Potassium  Nitrate. 


POTASSIUM  HYDROXIDE  135 


POTASSIUM    HYDROXIDE 

(Caustic  Potash;  Potassium  Hydrate) 
KOH.    Mol.  Wt.  56.11 

In  the  laboratory,  three  grades  of  potassium  hydroxide  are 
generally  used : 

1.  Potassium  Hydroxide,  Purest. 

2.  Potassium  Hydroxide,  Pure. 

3.  Potassium  Hydroxide,  Purified. 

These  three  preparations  differ  chiefly  in  their  content  of  chloride, 
sulphate,  silicate,  and  alumina. 


POTASSIUM  HYDROXIDE,  PUREST 

White,  very  hygroscopic  pieces  showing  a  crystalline  structure 
on  fracture.     The  preparation  contains  82  to  85  per  cent  of  KOH. 
TESTS  OF  PURITY 

Sulphates.  —  Dissolve  3  gin.  of  potassium  hydroxide  in  50  c.c.  of  water,  add 
10  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  then  add  barium  chloride  solution. 
No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indi- 
cating less  than  O.OC4  per  cent  SO3.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  hydroxide  in  20  c.c.  of  water,  and 
add  5  c.c.  of  nitric  acid,  followed  by  a  few  drops  of  silver  nitrate  solution.  Not 
more  than  a  slight  opalescent  turbidity  should  develop  within  one  minute 
(Indicating  less  than  0.0025  per  cent  Cl.) 

Nitrates.  —  Dissolve  2  gm.  of  potassium  hydroxide  and  a  granule  of  sodium 
chloride  in  10  c.c.  of  16  per  cent  sulphuric  acid,  and  add  1  drop  of  1  :  1000 
indigo  solution  and  10  c.c.  of  concentrated  sulphuric  acid.  The  blue  color  of 
the  mixture  should  not  disappear  on  agitation.  (Indicating  less  than  0.0016 
1  tr  cent  N2O5.) 

Nitrogen  as  Nitrates,  Nitrites,  Ammonia,  etc.  —  Dissolve  50  gm.  of  potas- 
sium hydroxide  in  100  c.c.  of  water  in  a  distillation  flask.  To  the  solution  add  2 
gm.  of  Devarda's  metal,  connect  the  flask  with  a  bulb  tube,  condenser,  and  a 
receiver  containing  2  to  3  c.c.  of  fifth-normal  hydrochloric  acid  solution  and  10 
c.c.  of  water;  allow  to  stand  one  to  two  hours,  and  then  distil  off  about  50  c.c. 
Titrate  the  distillate  with  fifth-normal  potassium  hydroxide  solution,  using 
methyl  orange  as  the  indicator.  At  most  0.2  c.c.  of  fifth-normal  hydrochloric 
acid  solution  should  have  been  required  to  neutralize  the  ammonia.  (Indi- 
cating not  more  than  0.00112  per  cent  N.) 

Nitrites.  —  The  solution  of  1  gm.  of  potassium  hydroxide  in  10  c.c.  of  water 
and  10  c.c.  of  diluted  sulphuric  acid  should  not  be  colored  blue  on  adding  zinc 
iodide-starch  solution.  (Indicating  less  than  0.00011  per  cent  N2O3.) 

Phosphates.  —  Dissolve  5  gm.  of  potassium  hydroxide  in  50  c.c.  of  water 
and  add  30  c.c.  of  nitric  acid,  followed  by  25  c.c.  of  a  solution  of  ammonium 


136  CHEMICAL  REAGENTS 


molybdate  in  nitric  acid.  This  mixture  should  deposit  no  yellow  precipitate  on 
standing  two  hours  at  about  40°  C.  (Indicating  less  than  0.004  per  cent  P2O;.) 

Silicates.  —  Dissolve  5  gm.  of  potassium  hydroxide  in  25  c.c.  of  water  in  a 
platinum  dish,  add  25  c.c.  of  hydrochloric  acid,  and  then  evaporate  to  dryness 
on  the  water-bath.  Dry  the  residue  for  half  an  hour  at  about  120°  C.,  and  then 
dissolve  it  in  10  c.c.  of  hydrochloric  acid  and  90  c.c.  of  water.  Any  insoluble 
residue  should  be  filtered  off,  washed,  and  ignited.  Its  weight  should  not  exceed 
0.001  gm.  (Indicating  not  more  than  0.02  per  cent  SiOo.) 

Aluminum,  Calcium,  and  Heavy  Metals. —  5  gm.  of  potassium  hydroxide  should 
yield  a  clear  and  colorless  solution  with  10  c.c.  of  water.  To  this  solution  add 
25  c.c.  of  acetic  acid  (sp.gr.  1.041),  followed  by  10  c.c.  of  ammonia  water,  dilute 
with  55  c.c.  of  water,  and  heat  the  fluid  on  the  water-bath  until  the  odor  of 
ammonia  has  disappeared.  Now  add  a  few  drops  of  ammonia  water,  and  allow 
to  stand  fifteen  hours.  At  the  end  of  this  time  there  should  be  no  precipitate, 
or,  at  most,  only  an  exceedingly  slight,  flocculent  precipitate.  In  the  latter 
case  the  precipitate  is  collected  by  filtration,  washed,  and  ignited.  Its  weight 
should  not  exceed  0.001  gm.  (Indicating  not  over  0.0106  per  cent  Al.)  The 
following  tests  are  now  carried  out  with  the  filtrate: 

To  50  c.c.  add  ammonium  oxalate  solution.  No  precipitate  of  calcium  oxalate 
should  form  within  two  hours.  (Indicating  less  than  0.012  per  cent  Ca.) 

To  50  c.c.  add  a  few  drops  of  ammonium  sulphide  solution.  Neither  a  green 
or  a  brown  color  nor  a  precipitate  should  appear.  (Indicating  no  heavy  metals 
present.)  't 

Substances  Insoluble  in  Alcohol.  —  Dissolve  5  gm.  of  potassium  hydroxide 
in  10  c.c.  of  water  and  mix  the  solution  with  50  c.c.  of  85  per  cent  alcohol.  There 
should  be  no  precipitate  within  one  hour.  (Indicating  none  present.) 

Quantitative  Determination,  and  Determination  of  the  Potassium  Carbonate 
Content.  —  Titrate  a  cold  solution  of  1  gm.  of  potassium  hydroxide  in  100  c.c. 
of  water  with  normal  solution  of  hydrochloric  acid,  using  phenolphthlein  as  the 
indicator.  At  least  14.8  c.c.  of  the  acid  should  be  necessary  to  destroy  the  red 
color.  (First  titration.)  Now  add  1"  drop  of  methyl  orange,  and  titrate  further 
until  the  color  again  changes  to  red.  In  this  second  titration,  not  more  than 
0.2  c.c.  of  the  acid  should  be  required.  (Indicating  not  more  than  2.76  per  cent 
K2C03).* 

1  c.c.  of  normal  HC1  =0.05611  gm.  of  KOH,  log.  74904. 

1  c.c.  of  normal  HC1  =0.0691  gm.  of  K2CO3,  log.  83948. 

II 
POTASSIUM   HYDROXIDE,  PURE 

White,  very  hygroscopic  sticks  or  pieces,  exhibiting  a  crystalline 
fracture.     The  preparation  contains  at  least  80  per  cent  of  KOH. 


*  From  the  results  of  both  titrations,  the  content  of  potassium  hydroxide 
and  potassium  carbonate  are  calculated  as  follows: 

The  result  of  the  second  titration  multiplied  by  two  gives  the  number  of 
cubic  centimeters  which  are  necessary  to  neutralize  the  potassium  carbonate 
originally  present. 

On  subtracting  the  number  of  cubic  centimeters  required  in  the  second 
titration  from  the  number  of  cubic  centimeters  used  in  the  first  titration,  the 
remainder  gives  the  number  of  cubic  centimeters  which  were  required  to  neutralize 
the  potassium  hydroxide. 


POTASSIUM  HYDROXIDE  137 


TESTS   OF  PURITY 

Sulphates,  Nitrates  and  Nitrogen  as  Nitrates,  Nitrites,  Ammonia,  etc.  —  The 
tests  are  carried  out  as  detailed  under  Potassium  Hydroxide,  Purest. 

Chlorides. — Dissolve  1  gm.  of  potassium  hydroxide  in  20  c.c.  of  water,  and  add 
5  c.c.  of  nitric  acid  and  a  few  drops  of  silver  nitrate  solution.  An  ppalescence 
may  develop,  but  no  precipitate  should  form  immediately.  (Indicating  less 
than  0.005  per  cent  Cl.) 

Silicates.  —  Dissolve  5  gm.  of  potassium  hydroxide  in  25  c.c.  of  water  and 
25  c.c.  of  hydrochloric  acid  in  a  platinum  dish,  and  evaporate  to  dryness  on  the 
water-bath.  Dry  the  residue  for  half  an  hour  at  about  120°  C.,  then  treat  it 
with  10  c.c.  of  hydrochloric  acid  and  90  c.c.  of  water,  filter,  wash,  and  ignite 
any  undissolved  residue.  The  weight  of  the  latter  should  not  exceed  0.003  gm. 
(Indicating  not  more  than  0.06  per  cent  SiO2.) 

Aluminum,  Calcium,  and  Heavy  Metals.  —  5  gm.  of  potassium  hydroxide 
should  completely  dissolve  in  20  c.c.  of  water,  affording  a  clear  and  colorless 
solution.  Add  to  the  solution  25  c.c.  of  acetic  acid  (sp.gr.  1.041)  followed  by 
10  c.c.  of  ammonia  water,  dilute  with  55  c.c.  of  water,  heat  the  solution  on  the 
water-bath  until  the  odor  of  ammonia  has  disappeared,  and  add  a  few  drops 
more  of  ammonia  water.  On  standing  fifteen  hours  only  slight  precipitation 
should  occur.  The  precipitate  is  filtered  off,  washed  and  ignited.  Its  weight 
should  not  exceed  0.003  gm.  (Indicating  not  more  than  0.032  per  cent  Al.)  No 
precipitate  should  appear  within  two  minutes  on  the  addition  of  ammonium 
oxalate  solution  to  the  filtrate  (indicating  less  than  0.04  per  cent  Ca) ;  and  the 
addition  of  ammonium  sulphide  solution  should  cause  at  most  a  slight  green 
coloration,  but  in  no  case  should  a  brown  color  or  a  precipitate  appear.  (Indi- 
cating at  most  a  trace  of  heavy  metals.) 

Quantitative  Determination,  and  Determination  of  the  Potassium  Carbonate 
Content.  —  Dissolve  1  gm.  of  potassium  hydroxide  in  100  c.c.  of  water,  and 
titrate  the  cold  solution  with  normal  solution  of  hydrochloric  acid,  using  phenol- 
phthalein  as  the  indicator.  At  least  14.5  c.c.  of  the  acid  should  be  necessary  to 
destroy  the  red  color.  Now  add  1  drop  of  methyl  orange  solution,  and  titrate 
further  until  the  color  again  changes  to  red.  In  this  second  titration  not  more 
than  0.30  c.c.  of  the  acid  should  be  required.  (Indicating  not  more  than  4.15 
per  cent  K2CO3).* 

1  c.c.  of  normal  HC1  =  0.05611  gm.  of  KOH,  log.  74904. 

1  c.c.  of  normal  HC1  =  0.0691  gm.  of  K2CO3,  log.  83948. 

Ill 
POTASSIUM   HYDROXIDE,  PURIFIED 

White,  very  hygroscopic  sticks  or  pieces  which  exhibit  a  crystalline 
fracture.  The  preparation  should  contain  at  least  80  per  cent  of  KOH. 

TESTS   OF  PURITY 

Nitrates.  —  Dissolve  2  gm.  of  potassium  hydroxide  and  a  granule  of  sodium 
chloride  in  10  c.c.  of  diluted  sulphuric  acid,  and  add  1  drop  of  1  :  1000  indigo 
solution  and  10  c.c  of  concentrated  sulphuric  acid.  The  blue  color  of  the 
mixture  should  not  disappear  on  agitation.  (Indicating  less  than  0.0016  per 
cent  N2O5.) 


*  See  the  note  under  Potassium  Hydroxide,  Purest. 


138  CHEMICAL  REAGENTS 


Aluminum,  Calcium,  and  Heavy  Metals.  —  2.5  gm.  of  potassium  hydroxide 
should  completely  dissolve  in  10  c.c.  of  water,  yielding  a  clear  and  colorless  solu- 
tion. Dilute  the  solution  with  50  c.c.  of  water  and  add  15  c.c.  of  acetic  acid 
(sp.gr.  1.041),  followed  by  10  c.c.  of  ammonia  water;  no  precipitate  should  form. 
(Indicating  less  than  0.1  per  cent  Al.)  The  solution  so  tested  should  not  exhibit 
an  immediate  turbidity  on  adding  ammonium  oxalate  solution  (indicating  less 
than  0.1  per  cent  Ca);  and  on  the  addition  of  ammonium  sulphide  solution 
it  should  acquire  at  most  a  slight  green  color.  (Indicating  at  most  a  trace  of 
heavy  metals.) 

Quantitative  Determination  and  Determination  of  the  Potassium  Carbonate 
Content.  —  The  determinations  are  made  as  detailed  under  Potassium  Hydroxide, 
Pure.  The  content  of  potassium  carbonate  should  not  exceed  5  per  cent. 

POTASSIUM  HYDROXIDE  SOLUTIONS 

A  clear,  colorless  liquid,  of  specific  gravity  1.3,  and  containing 
about  32  per  cent  of  potassium  hydroxide. 

Also  a  similar  solution  having  a  specific  gravity  1.138  to  1.140 
and  containing  about  15  per  cent  of  potassium  hydroxide. 

TESTS   OF  PURITY 

The  tests  and  the  quantitative  determination,  as  given  under  Potassium 
Hydroxide,  Pure,  are  to  be  made  on  each  solution.  But,  of  the  solution  having 
sp.gr.  1.3,  use  2  c.c.  (2.6  gm.)  in  place  of  each  gram  of  the  solid  hydroxide  referred 
to.  And,  of  the  solution  having  sp.gr.  1.138  to  1.140,  use  5  c.c.  (5.7  gm.). 

POTASSIUM  IODATE 
KIO3.    Mol.  Wt.  214.02 

A  white,  crystalline  powder,  soluble  in  13  parts  of  cold,  and  in 
5  parts  of  boiling,  water.  The  1  :  20  aqueous  solution  should  be 
clear  and  neutral  to  litmus  paper.  The  preparation  contains  100 

per  cent  of  KIOs. 

TESTS  OF  PURITY 

Free  Acids.  —  Dissolve  about  0.5  gm.  of  potassium  iodate  in  about  20  c.c.  of 
boiled  water,  and  add  a  small  crystal  of  neutral  potassium  iodide  and  a  few 
drops  of  starch  solution.  The  liquid  should  not  acquire  a  blue  color  within 
thirty  seconds.  (Indicating  less  than  0.07  per  cent  as  HIO3.) 

Iodides.  —  Dissolve  1  gm.  of  potassium  iodate  in  20  c.c.  of  water,  add  3  to  5 
drops  of  diluted  sulphuric  acid,  and  shake  the  mixture  with  chloroform.  The 
latter  should  not  acquire  a  violet  color.  (Indicating  less  than  0.0015  per  cent  I.) 

Chlorates.  —  This  test  is  to  be  carried  out  as  described  under  Potassium 
Biniodate.  (Indicating  less  than  0.15  per  cent  CUOs.) 

Quantitative  Determination.  —  Dissolve  0.10  to  0.15  gm.  of  potassium  iodate 
previously  dried  over  sulphuric  acid,  in  20  c.c.  of  water,  add  3  gm.  of  potassium 
iodide  and  5  c.c.  of  hydrochloric  acid,  and  titrate  the  liberated  iodine  with  deci- 
normal  sodium  thiosulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3=  0.003567  gm.  of  KIO3,  log.  55230. 


POTASSIUM  IODIDE  139 

POTASSIUM  IODIDE 
KI.    Mol.  Wt.  166.02 

White,  cubical  crystals,  not  becoming  moist  on  contact  with  air. 
Potassium  iodide  is  soluble  in  about  0.75  part  of  water,  in  about  12 
parts  of  85  per  cent  alcohol,  and  in  40  parts  of  absolute  alcohol. 
TESTS   OF  PURITY 

Potassium  Carbonate.  —  Potassium  iodide  when  crushed  and  placed  upon 
moistened  red  litmus  paper  should  not  immediately  color  the  latter  violet-blue. 

On  adding  to  a  solution  of  0.5  gm.  of  potassium  iodide  in  10  c.c.  of  water 
1  drop  of  phenolphthalein  solution,  no  red  color  should  develop.  (Indicating 
less  than  0.08  per  cent  K2CO3.) 

Heavy  Metals.  —  20  c.c.  of  the  1  :  20  aqueous  solution  of  potassium  iodide 
should  afford  no  reaction  with  hydrogen  sulphide  water;  and  on  further  addition 
of  ammonia  water  neither  a  green  or  brown  color  should  develop,  nor  should 
a  precipitate  form.  (Indicating  none  present.) 

Sulphates.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should  afford  no  reaction 
with  barium  chloride  solution.  (Indicating  less  than  0.01  per  cent  SO3.) 

Cyanides.  —  On  adding  to  20  c.c.  of  the  1  :  20  aqueous  solution  a  granule  of 
ferrous  sulphate,  1  drop  of  ferric  chloride  solution,  and  5  c.c.  of  sodium  hydroxide 
solution  (sp.gr.  1.3),  then  heating  the  mixture  to  50°  to  60°  C.,  and  adding  10 
c.c.  of  hydrochloric  acid,  no  blue  color  should  develop.  (Indicating  less  than 
0.03  per  cent  CN.) 

lodates  and  Ferric  Salts.  —  The  1  :  20  aqueous  solution,  freshly  prepared 
with  recently  boiled  and  cooled  water,  should  not  within  one  minute  acquire  a 
blue  color  on  the  addition  of  starch  solution  and  2  or  3  drops  of  diluted  sulphuric 
acid.  (Indicating  less  than  0.001  per  cent  I2O5,  or  less  than  0.05  per  cent  Fe'".) 

Nitrates.  —  On  heating  1  gm.  of  potassium  iodide  with  5  c.c.  of  sodium 
hydroxide  solution  and  a  mixture  of  0.5  gm.  of  zinc  dust  and  0.5  gm.  of  powdered 
iron,  no  vapors  of  ammonia  should  be  evolved  (to  be  ascertained  by  moist  litmus 
paper).  (Indicating  less  than  0.0016  per  cent  N2O5.) 

Quantitative  Determination,  and  Test  for  Excess  of  Potassium  Chloride. *  — 
Dissolve  0.5  gm.  of  potassium  iodide  in  25  c.c.  of  water,  add  35  c.c.  of  deci- 
normal  solution  of  silver  nitrate,  and  shake  until  the  precipitate  has  coagulated. 
Add  2  c.c.  of  nitric  acid  and  5  c.c.  of  cold,  saturated  solution  of  ferric  ammonium 
sulphate,  and  titrate  with  decinormal  solution  of  ammonium  sulphocyanate. 
Not  less  than  4.7  c.c.  and  not  more  than  4.9  c.c.  of  the  latter  should  be  required 
to  produce  a  permanent  red  color.  (Indicating  at  most  0.5  per  cent  KC1.) 

1  c.c.  of  decinormal  AgNO3  =  0.016602  gm.  of  KI,  log.  22016. 

POTASSIUM  IODIDE,  NEUTRAL 
TESTS  OF  PURITY 

Neutrality.  —  Dissolve  10  gm.  of  the  neutral  potassium  iodide  in  50  c.c.  of 
water,  in  a  stoppered,  flint-glass  bottle,  overlay  with  30  c.c.  of  ether,  and  add 
3  drops  of  iodeosin  solution.  After  vigorously  shaking,  the  aqueous  layer  will 
exhibit  a  pale-red  color  which  disappears  on  adding  1  drop  of  decinormal  hydro- 
chloric acid  solution  and  thoroughly  shaking.  (Indicating  less  than  0.003  per 
cent  alkali  as  KOH.) 

*  Potassium  iodide  nearly  always  contains  potassium  chloride.  The  amount 
of  the  latter  present  when  this  test  is  complied  with,  is  at  most  0,5  per  cent, 


MO  CHEMICAL  REAGENTS 


Should  the  water  which  has  been  used  for  making  the  solution  of  potassium 
iodide  have  an  alkaline  reaction  to  iodeosin,  it  must  be  first  rendered  neutral  to  it. 

further  Tests.  —  The  tests  as  given  under  Potassium  Iodide  are  also  to  be 
made,  and  in  the  manner  there  described. 

POTASSIUM   NITRATE 
KNO3.     Mol.  Wt.  ioi.li 

Colorless,  transparent,  prismatic  crystals,  or  crystalline  powder, 
permanent  in  air,  and  soluble  in  4  parts  of  cold,  and  in  about  0.5 
part  of  boiling,  water;  almost  insoluble  in  alcohol.  The  aqueous 
solution  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Sulphates.  —  Dissolve  3  gm.  of  potassium  nitrate  in  60  c.c.  of  water,  and  add 
1  c.c.  of  hydrochloric  acid  followed  by  barium  chloride  solution.  No  precipitate 
of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating  less  than 
0.0025  per  cent  SO?.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  nitrate  in  20  c.c.  of  water,  acidulate 
with  1  c.c.  of  nitric  acid  and  add  silver  nitrate  solution.  No  change  should 
occur.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Chlorates  and  Perchlorates.  —  Gently  ignite  1  gm.  of  potassium  nitrate, 
dissolve  the  melt  in  20  c.c.  of  water,  add  1  c.c.  of  nitric  acid  and  some  silver 
nitrate  solution.  No  change  should  appear.  (Indicating  less  than  0.0005  per 
cent  as  Cl.) 

Calcium  and  Heavy  Metals.  —  The  solution  of  3  gm.  of  potassium  nitrate 
in  50  c.c.  of  water  should  not  be  affected  either  by  hydrogen  sulphide  water  or 
by  ammonia  water  followed  by  ammonium  oxalate  solution  (indicating  less  than 
0.01  per  cent  Ca);  and  after  the  addition  of  ammonium  sulphide  solution 
neither  a  green  or  brown  color,  nor  a  precipitate,  should  appear.  (Indicating 
no  heavy  metals  present.) 

Iron.  —  20  c.c.  of  the  1  :  20  aqueous  solution,  acidulated  with  1  c.c.  of  hydro- 
chloric acid  should  not  be  reddened  by  potassium  sulphocyanate  solution. 
(Indicating  less  than  0.0008  per  cent  Fe.) 

Nitrites.  —  Dissolve  1  gm.  of  potassium  nitrate  in  20  c.c.  of  water,  acidulate 
with  1  c.c.  of  16  per  cent  sulphuric  acid,  and  add  1  c.c.  of  a  freshly  prepared, 
colorless  1  :  200  solution  of  metaphenylenediamine  hydrochloride.  *  No  yellow 
or  yellowish-brown  color  should  develop.  (Indicating  less  than  0.00055  per  cent 
N203.) 

POTASSIUM  NITRITE 
KN02.     Mol.  Wt.  85.11 

White,  or  slightly  yellowish,  tough,  hygroscopic,  sticks,  which 
are  very  easily  soluble  in  water.  The  aqueous  solution  is  alkaline 
to  litmus  paper.  The  preparation  contains  at  least  90  per  cent  of 
KN02. 

*  Should  the  solution  of  metaphenylenediamine  hydrochloride  have  a  color, 
it  is  to  be  decolorized  before  using  by  warming  with  freshly  ignited  animal 
charcoal. 


POTASSIUM  OXALATE 


TESTS  OF  PURITY 

Heavy  Metals.  —  Dissolve  1  gm.  of  potassium  nitrite  and  1  gm.  of  ammonium 
chloride  in  5  c.c.  of  water,  evaporate  to  dryness  on  the  water-bath,  and  dissolve 
the  residue  in  10  c.c.  of  water.  This  solution  should  not  be  affected  by  hydrogen 
sulphide  water;  and  after  adding  ammonia  water  and  ammonium  sulphide 
solution  neither  a  green  or  brown  color  nor  a  precipitate  should  appear.  (Indi- 
cating none  present.) 

Chlorides.  —  The  solution  of  1  gm.  of  potassium  nitrite  in  20  c.c.  of  water 
should  acquire  at  most  a  slight  opalescence  on  the  addition  of  5  c.c.  of  nitric 
acid  and  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent  Cl.) 

Sulphates.  —  On  adding  to  20  c.c.  of  the  1  :  20  aqueous  solution  5  c.c.  of 
concentrated  nitric  acid,  boiling  to  expel  oxides  of  nitrogen,  and  then  adding 
barium  nitrate  solution,  no  turbidity  should  develop.  (Indicating  less  than 
0.175  per  cent  SO3.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  nitrite  in  water 
and  dilute  to  100  c.c.  Allow  20  c.c.  of  the  nitrite  solution  to  run  slowly  into  a 
mixture  of  50  c.c.  of  decinormal  potassium  permanganate  solution,  300  c.c.  of 
water  and  25  c.c.  of  16  per  cent  sulphuric  acid,  while  constantly  shaking. 
After  ten  minutes  add  3  gm.  of  potassium  iodide  to  the  mixture,  and  titrate  the 
liberated  iodine  with  decinormal  sodium  thiosulphate  solution,  using  starch 
solution  as  indicator. 

1  c.c.  of  decinormal  KMnO4= 0.0042555  gm.  of  KN02,  log.  62895. 

POTASSIUM   OXALATE,  NEUTRAL 

K2C204+H20.    Mol.  Wt.  184.22 
Rhombic  prisms,  soluble  in  3  parts  of  water. 
TESTS   OF  PURITY 

Neutrality.  —  The  solution  of  10  gm.  of  potassium  oxalate  in  100  c.c.  of 
water  should  not  be  changed  by  phenolphthalein  solution  (indicating  no  alkali 
present) ;  but  on  adding  further  0.1  c.c.  of  decinormal  potassium  hydroxide  solu- 
tion, a  red  color  should  appear.  (Indicating  less  than  0.0045  per  cent  acid  as 
H2C204.) 

Sulphates.  —  Boil  a  solution  of  5  gm.  of  potassium  oxalate  in  200  c.c.  of  water, 
and  add  10  c.c.  of  hydrochloric  acid  followed  by  barium  chloride  solution.  No 
precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating 
less  than  0.005  per  cent  SO3.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  oxalate  in  25  c.c.  of  water,  and  add 
10  c.c.  of  nitric  acid  and  two  or  three  drops  of  silver  nitrate  solution.  At  most 
a  slight  opalescence  should  develop  on  snaking.  (Indicating  less  than  0.0025 
per  cent  Cl.) 

Heavy  Metals.  —  To  a  solution  of  1  gm.  of  potassium  oxalate  in  25  c.c.  of 
water,  add  hydrogen  sulphide  water.  The  solution  should  remain  unchanged. 
On  now  adding  ammonia  water  and  a  few  drops  of  ammonium  sulphide  solu- 
tion to  the  liquid,  no  green  or  brown  color  should  develop,  nor  should  a  precipi- 
tate form.  (Indicating  none  present.) 

Quantitative  Determination.  —  Dissolve  1  gm,  of  potassium  oxalate  in  water 
and  dilute  to  100  c.c.  To  25  c.c.  of  this  solution  add  6  to  8  c.c.  of  concentrated 
sulphuric  acid,  heat  the  liquid  to  about  60°  C.,'and  titrate  with  decinormal 
potassium  permanganate  solution. 

1  c.c.  of  decinormal  KMn04  =  0.009211  gm.  of  K2C2O4+H2O,  log.  96431. 


142  CHEMICAL  REAGENTS 


POTASSIUM  PERCHLORATE 

KC1O4.     Mol.  Wt.  138.56 

Colorless,  rhombic  prisms,  soluble  in  about  65  parts  of  cold, 
and  in  8  parts  of  boiling,  water,  and  insoluble  in  alcohol.  Potas- 
sium perchlorate  is  neither  colored  by  concentrated  sulphuric  acid 
nor  decomposed  by  hydrochloric  acid  (difference  from  potassium 

chlorate.) 

TESTS  OF  PURITY 

Chlorides.  —  20  c.c.  of  the  1  :  20  solution  in  hot  water  should  develop  at 
most  a  slight  opalescence  on  the  addition  of  silver  nitrate  solution.  (Indicating 
less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  20  c.c.  of  the  1  :  20  solution  in  hot  water  should  not  be 
affected  by  hydrogen  sulphide  water.  After  adding  a  few  drops  of  ammonium 
sulphide  solution  neither  a  green  or  brown  color  nor  a  precipitate  should  appear. 
(Indicating  none  present.) 

Nitrates.  —  On  heating  a  mixture  of  1  gm.  of  potassium  perchlorate  with 
5  c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3)  and  a  mixture  of  0.5  gm.  of  zinc 
dust  and  0.5  gm.  of  powdered  iron,  no  vapors  of  ammonia  should  be  evolved 
(to  be  ascertained  by  moist  litmus  paper.)  (Indicating  less  than  0.0016  per 
cent  N2O5.) 

Sulphates.  —  On  adding  barium  chloride  solution  to  20  c.c.  of  the  1  :  20 
solution  in  hot  water,  no  change  should  appear.  (Indicating  less  than  0.005 
per  cent  SO3.) 

Calcium.  —  Qn  adding  ammonium  oxalate  solution  to  20  c.c.  of  the  1  :  20 
solution  of  potassium  perchlorate  in  hot  water,  no  change  should  occur.  (Indi- 
cating less  than  0.02  per  cent  Ca.) 

Quantitative  Determination.  —  Fuse  in  a  nickel  crucible  a  mixture  of  1  gm. 
of  powdered  potassium  perchlorate  and  5  gm.  of  powdered  sodium  nitrite  free 
from  chlorine,  and  maintain  in  a  state  of  fusion  for  about  half  an  hour  at  a  low 
temperature.  When  cool,  dissolve  the  melt  in  water  and  dilute  to  500  c.c. 
Add  to  100  c.c.  of  this  solution  20  c.c.  of  decinormal  silver  nitrate  solution  and 
20  c.c.  of  nitric  acid,  and  warm  the  mixture  on  the  water-bath  until  the  red 
vapors  have  disappeared.  Now  add  5  c.c.  of  a  cold  saturated  solution  of  ferric 
ammonium  sulphate  and  titrate  with  decinormal  solution  of  ammonium  sulpho- 
cyanate. 

1  c.c.  of  decinormal  AgNO3  =  0.013856  gm.  of  KC1O4,  log.  14163. 

POTASSIUM    PERMANGANATE 

KMnO4.    Mol.  Wt.  158.03 

I 
POTASSIUM  PERMANGANATE 

Dark-violet,  almost  black  prisms,  exhibiting  a  steel-blue  luster; 
soluble  in  16  parts  of  cold,  and  in  3  parts  of  boiling,  water.  The 
1  :  1000  aqueous  solution  is  neutral  to  litmus  paper. 


POTASSIUM  PERMANGANATE  143 


TESTS   OF  PURITY 

Sulphates  and  Chlorides.  —  Boil  0.5  gm.  of  potassium  permanganate 
with  a  mixture  of  2  c.c.  of  95  per  cent  alcohol  and  25  c.c.  of  water,  and  filter. 
The  nitrate  should  be  colorless,  and,  after  adding  to  it  2  c.c.  of  nitric  acid, 
neither  barium  nitrate  nor  silver  nitrate  solutions  should  cause  more  than  a 
slight  opalescence.  (Indicating  less  than  0.03  per  cent  SOs,  and  less  than  0.004 
per  cent  Cl.) 

Nitrates.  —  Add  gradually  1  gm.  of  crystallized  oxalic  acid  to  a  solution 
of  0.5  gm.  of  potassium  permanganate  in  5  c.c.  of  water  heated  to  50°  to  60°  C., 
then  heat  to  boiling,  and  filter.  On  overlaying  1  c.c.  of  ferrous  sulphate  solution 
on  a  cooled  mixture  of  2  c.c.  of  the  clear  colorless  filtrate  and  2  c.c.  of  con- 
centrated sulphuric  acid,  no  dark-colored  zone  should  form  at  the  contact-sur- 
faces of  the  two  liquids.  (Indicating  less  than  0.08  per  cent  ^Os.) 

Chlorates.  —  Heat  2  gm.  of  potassium  permanganate  in  a  platinum  crucible, 
and  gradually  add  small  pieces  of  paraffin  until  no  more  glowing  is  observed. 
When  cold,  the  residue  is  treated  with  20  c.c.  of  water,  filtered,  and  5  c.c.  of 
nitric  acid  and  silver  nitrate  solution  are  added  to  the  colorless  filtrate.  The 
liquid  should  develop  at  most  a  slight  opalescence.  (Indicating  less  than  0.0016 
per  cent  C^Os.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  permanganate 
in  water  and  dilute  to  100  c.c.  Dilute  10  c.c.  of  this  solution  with  100  c.c.  of 
water,  add  2  gm.  of  potassium  iodide  and  20  c.c.  of  diluted  sulphuric  acid,  and 
titrate  with  decinormal  solution  of  sodium  thiosulphate. 

1  c.c.  of  decinormal  Na2S2O3  =  0.003 1606  gm.  of  KMnO4,  log.  49977. 

II 
POTASSIUM    PERMANGANATE,    FREE    FROM    SULPHATES 

The  preparation  contains  about  100  per  cent  of  KMn04. 

TESTS   OF  PURITY 

Sulphates.  —  The  solution  of  3  gm.  of  potassium  permanganate  in  150  c.c. 
of  water  with  15  c.c.  of  95  per  cent  alcohol  (or  a  little  hydrogen  peroxide,  30 
per  cent),  heated,  if  necessary,  until  perfectly  decolorized,  should  yield  a  filtrate, 
which,  on  the  addition  of  2  c.c.. of  hydrochloric  acid  and  barium  chloride  solution, 
should  afford  no  precipitate  of  barium  sulphate  on  standing  fifteen  hours.  (Indi- 
cating less  than  0.003  per  cent  SO3.) 

Further  Tests.  —  The  other  tests  and  the  quantitative  determination  as 
given  under  Potassium  Permanganate  are  also  to  be  made. 

POTASSIUM  PERSULPHATE 
K2S2O8.     Mol.  Wt.  270.34 

Colorless  crystals,  soluble  in  50  parts  of  cold,  and  4  parts  of 
boiling,  water.  The  aqueous  solution  is  neutral  to  litmus  paper. 
Potassium  persulphate  gradually  decomposes,  evolving  oxygen. 
The  preparation  contains  at  least  95  per  cent  of 


144  CHEMICAL  REAGENTS 


TESTS   OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  potassium  persulphate  in  50  c.c.  of 
water  should  become  at  most  slightly  opalescent  on  adding  3  to  5  drops  of  silver 
nitrate  solution.  More  silver  nitrate  solution  produces  a  black  precipitate 
which  masks  the  chloride  reaction.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  Dissolve  4  gm.  of  potassium  persulphate  in  50  c.c.  of 
sulphurous  acid  (sp.gr.  1.029  to  1.035)  with  the  aid  of  heat,  evaporate  the  solu- 
tion to  dryness  on  the  water-bath,  and  dissolve  the  residue  in  40  c.c.  of  water. 

20  c.c.  of  this  solution  should  not  be  affected  by  hydrogen  sulphide  water. 
(Indicating  none  present.) 

Another  portion  of  20  c.c.  of  the  solution  should  not  appear  changed  on 
adding  ammonia  water  to  alkaline  reaction;  and  on  the  further  addition  of  a  few 
drops  of  ammonium  sulphide  solution,  at  most  a  green  color  may  develop,  but 
no  precipitate  should  form.  (Indicating  at  most  a  trace  present.) 

Quantitative  Determination.  —  Weigh  into  a  100  c.c.  graduated  flask  1  gm. 
powdered  potassium  persulphate,  pour  over  the  sample  a  solution  of  5  gm.  of 
potassium  iodide  in  50  c.c.  of  water,  add  10  c.c.  of  diluted  sulphuric  acid,  let  the 
mixture  stand  about  a  half-hour  with  frequent  shaking,  fill  with  water  to  the 
mark  and  mix.  Titrate  20  c.c.  of  the  solution  with  decinormal  sodium  thio- 
sulphate  solution. 

1  c.c.  of  decinormal  Na2S2O3  =  0.013517  gm.  of  K2S2O8,  log.  13088. 

POTASSIUM   STANNOSULPHATE 
(Marignac's  Salt) 

K2Sn(SO4)2.     Mol.  Wt.  389.34 

White  crystals,  soluble  in  dilute  potassium  or  sodium  hydroxide 
solution,  and  in  hydrochloric  acid. 

TEST   OF  PURITY 

Quantitative  Determination.  —  Dissolve  1  gm.  of  potassium  stannosulphate, 
5  gm.  of  sodium  bicarbonate,  and  5  gm.  of  potassium  and  sodium  tartrate  in 
water,  dilute  to  100  c.c.,  and  titrate  50  c.c.  of  the  solution  with  decinormal  iodine 
solution,  using  starch  solution  as  the  indicator. 

1  c.c.  of  decinormal  1=0.019467  gm.  of  K2Sn(SO4)2,  log.  28930. 

POTASSIUM  SULPHATE 
K2SO4.     Mol.  Wt.  174.36 

White,  hard  crystals,  soluble  in  10  parts  of  cold,  and  in  4  parts 
of  boiling,  water,  but  insoluble  in  alcohol.  The  aqueous  solution 
is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Chlorides,  Heavy  Metals  (Fe,  Cu),  Calcium  and  Magnesium.  —  20  c.c.  por- 
tions of  the  1  :  20  aqueous  solution  should  not  be  affected  by  hydrogen  sulphide 
water  (indicating  no  heavy  metals  present),  or  by  ammonium  oxalate,  silver 


POTASSIUM  SULPHIDE  145 


nitrate,  or  ammonum  phosphate  solutions.  (Indicating  less  than  0.001  per  cent 
Cl,  less  than  0.02  per  cent  Ca,  and  less  than  0.005  per  cent  Mg.) 

Iron.  —  The  solution  of  1  gm.  of  potassium  sulphate  in  20  c.c.  of  water  boiled 
with  a  few  drops  of  nitric  acid  should  remain  colorless  on  the  addition  of  potassium 
sulphocyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Nitrates.  —  Dissolve  1  gm.  of  potassium  sulphate  and  a  small  crystal  of 
sodium  chloride  in  10  c.c.  of  water,  add  1  drop  of  1  : 1000  indigo  solution  and 
10  c.c.  of  concentrated  sulphuric  acid.  The  blue  color  of  the  fluid  should  not 
disappear  on  shaking.  (Indicating  less  than  0.0032  per  cent  N2O5.) 

Ammonium  Salts.  —  Dissolve  1  gm.  of  potassium  sulphate  in  20  c.c.  of  water 
and  add  a  few  drops  of  Nessler's  solution.  At  most  a  slight  yellow  coloration 
should  result.  (Indicating  less  than  0.005  per  cent  NH3). 


POTASSIUM  SULPHIDE 

Leather-brown  or  yellowish-green  pieces,  which  deliquesce  in 
moist  air,  dissolve  in  2  parts  of  water  with  but  a  slight  residue,  and 
afford  alkaline,  yellowish-green  solutions.  On  adding  acetic  acid  to 
the  aqueous  solution,  hydrogen  sulphide  gas  is  copiously  evolved. 

TEST  OF  PURITY 

Nitrogen.  —  Dissolve  5  gm.  of  potassium  sulphide  in  100  c.c.  of  water  in  a 
distillation  flask,  add  2  gm.  of  Devarda's  metal  and  50  c.c.  of  sodium  hydroxide 
solution  (nitrogen-free,  sp.gr.  1.3),  connect  the  flask  with  a  bulb-tube,  condenser, 
and  a  receiver  containing  2  to  3  c.c.  of  fifth-normal  solution  of  hydrochloric  acid. 
After  one  to  two  hours  distil  off  about  50  c.c.  and  titrate  the  distillate  with  fifth- 
normal  solution  of  potassium  hydroxide,  using  methyl  orange  as  indicator.  The 
amount  of  fifth-normal  acid  solution  found  to  have  been  neutralized  by  the 
ammonia  should  not  be  more  than  0.2  c.c.  (Indicating  not  more  than  0.0112 
per  cent  N.) 

POTASSIUM   SULPHIDE  SOLUTION 

The  solution  contains  5  per  cent  of  K2S,  and  is  intended  for  use 
in  detei  mining  nitrogen  according  to  Kjeldahl. 

TEST  OF  PURITY 

Nitrogen.  —  Mix  100  c.c.  of  the  potassium  sulphide  solution  in  a  distilling 
flask  with  2  gm.  of  Devarda's  metal  and  50  c.c.  of  nitrogen-free  sodium  hydroxide 
solution  (sp.gr.  1.3)  and  connect  the  flask  with  a  bulb-tube,  condenser,  and  a 
receiver  containing  10  c.c.  of  water  and  2  to  3  c.c.  of  fifth-normal  solution  of 
hydrochloric  acid.  After  one  or  two  hours  distil  off  about  50  c.c.  and  titrate  the 
distillate  with  normal  solution  of  potassium  hydroxide,  using  methyl  orange 
as  the  indicator.  The  ammonia  distilled  over  should  not  have  neutralized  more 
than  0.2  c.c.  of  the  fifth-normal  acid  solution.  (Indicating  not  more  than 
0.00056  percent  N.) 


146  CHEMICAL  REAGENTS 

POTASSIUM  SULPHOCYANATE 

(Potassium  Thiocyanate) 
KSCN.    Mol.  Wt.  97.18. 

Colorless,  prismatic  crystals,  deliquescent  in  the  air,  and  easily 
soluble  in  water  and  in  alcohol.  The  1  :  20  aqueous  solution  is 
neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Substances  Insoluble  in  Alcohol.  —  1  gm.  of  potassium  sulphocyanate  should 
completely  dissolve  in  10  c.c.  of  boiling  absolute  alcohol,  and  yield  a  clear  solution. 
(Indicating  none  present.) 

Chlorides.  —  Dissolve  1  gm.  of  potassium  sulphocyanate  in  100  c.c.  of  water, 
add  25  c.c.  of  nitric  acid,  heat  on  the  water-bath  for  three  hours,  and  then  add 
silver  nitrate  solution.  At  most  a  slight  opalescence  should  appear.  (Indicating 
less  than  0.0025  per  cent  Cl.) 

Sulphates.  —  On  adding  to  a  solution  of  1  gm.  of  potassium  sulphocyanate 
in  20  c.c.  of  water,  a  few  drops  of  hydrochloric  acid  and  some  barium  chloride 
solution,  no  turbidity  should  be  observed  within  five  minutes.  (Indicating 
less  than  0.01  per  cent  SO3.) 

Heavy  Metals.  —  On  dissolving  1  gm.  of  potassium  sulphocyanate  in  20  c.c. 
of  water  and  adding  hydrogen  sulphide  water,  no  change  should  appear;  and  on 
adding  to  the  solution  a  few  drops  of  ammonium  sulphide  solution,  no  pre- 
cipitate should  form,  nor  should  a  green  or  brown  color  develop.  (Indicating  none 
present.) 

Iron.  —  The  solution  of  1  gm.  of  potassium  sulphocyanate  in  20  c.c.  of  water 
should  remain  perfectly  colorless  on  the  addition  of  0.5  c.c.  of  hydrochloric  acid. 
(Indicating  less  than  0.0004  per  cent  Fe.) 

Ammonium  Compounds.  —  On  heating  to  boiling  a  solution  of  3  gm.  of  potas- 
sium sulphocyanate  in  10  c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3),  no 
ammonia  should  be  evolved  (to  be  ascertained  by  means  of  moistened  litmus 
paper).  (Indicating  less  than  0.0011  per  cent  NH3.) 

POTASSIUM  SULPHYDRATE 

(Potassium  Hydrosulphide) 
2KSH+H2O.    Mol.  Wt.  162.37 

Colorless,  deliquescent  crystals*  easily  soluble  in  water  and  in 
alcohol.  The  solution  is  strongly  alkaline  to  litmus  paper. 

TEST   OF  PURITY 

Polysulphides.  —  The  solution  of  1  gm.  of  potassium  sulphydrate  in  20 
c.c.  of  water  should  be  colorless  and  clear.  On  acidulating  the  solution  with 


*  When  exposed  to  the  air,  the  preparation  rapidly  acquires  a  yellow  color 
by  taking  up  oxygen  with  the  formation  of  polysuphide.  It  should,  therefore, 
be  preserved  in  well-stoppered  bottles. 


POTASSIUM  TETRAOXALATE  147 

hydrochloric  acid,  hydrogen  sulphide  gas  is  generated  copiously,  and  the  fluid 
exhibits  a  slight  opalescent  turbidity.  No  separation  of  sulphur  should  occur. 
(Indicating  none  present.) 

POTASSIUM  TETRAOXALATE 
KHC2O4+H2C2O4+2H2O.     Mol.  Wt.  254.16 

Colorless,  triclinic  crystals,  soluble  in  55  parts  of  cold,  and  in  3 
parts  of  boiling,  water.    The  aqueous  solution  is  acid  to  litmus  paper. 
TESTS   OF  PURITY 

Chlorides.  —  Dissolve  1  gm.  of  potassium  tetraoxalate  in  25  c.c.  of  water 
and  10  c.c.  of  nitric  acid,  and  add  2  or  3  drops  of  silver  nitrate  solution.  After 
shaking,  the  solution  should  be  at  most  slightly  opalescent.  (Indicating  less 
than  0.0025  per  cent  Cl.) 

Sulphates.  —  Dissolve  4  gm.  of  potassium  tetraoxalate  in  200  c.c.  of  water, 
add  10  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  add  barium  chloride  solu- 
tion. No  precipitate  of  barium  sulphate  should  form  on  standing  fifteen  hours. 
(Indicating  less  than  0.0063  per  cent  SO3.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  potassium  tetraoxalate  in  25 
c.c.  of  warm  water  should  not  be  affected  by  hydrogen  sulphide  water;  and 
after  adding  5  c.c.  of  ammonia  water  and  a  few  drops  of  ammonium  sulphide 
solution,  neither  a  green  or  brown  color  should  develop,  nor  should  a  precipitate 
form.  (Indicating;  none  present.) 

Quantitative  Determination,  (a)  Acidimetric:  Dissolve  1  gm.  of  potassium 
tetraoxalate  in  water  and  dilute  to  100  c.c.  Titrate  50  c.c.  of  this  solution,  while 
boiling,  with  fifth-normal  potassium  hydroxide  solution,  using  phenolphthalein 
as  the  indicator. 

1  c.c.  of  fifth  normal  KOH  =  0.016944  gm.  of  KHC2O4+H2C2O4+2H2O, 
log.  22901. 

(6)  Oxidimetric:  To  25  C.GX  of  the  solution  made  for  test  (a),  add  6  to  8  c.c. 
of  concentrated  sulphuric  acid,  heat  the  liquid  to  about  60°  C.,  and  titrate  with 
decinormal  potassium  permanganate  solution. 

1  c.c.  of  decinormal  KMnO4  =  0.006354  gm.  of  KHC2O4+H2C2O4+2H2O, 
log.  80305. 

POTASSIUM  AND  SODIUM  TARTRATE 

(Rochelle  Salt;  Seignette  Salt) 
KNaC4H4O6+4H2O.     Mol.  Wt.  282.20 

Colorless,  transparent,  prismatic  crystals,  soluble  in  1.4  parts 
of  water,  and  yielding  a  solution  neutral  to  phenolphthalein. 

TESTS   OF  PURITY 

Calcium.  —  On  dissolving  1  gm.  of  potassium  and  sodium  tartrate  in  10  c.c. 
of  water,  and  adding  to  the  solution  5  c.c.  of  diluted  acetic  acid,  and  then  shaking 
for  a  few  minutes,  a  white,  crystalline  precipitate  forms.  On  filtering  off  the  lat- 
ter, diluting  the  filtrate  with  an  equal  volume  of  water,  and  then  adding  8  to  10 
drops  of  ammonium  oxalate  solution,  no  turbidity  should  develop  within  one 
minute.  (Indicating  Jess  than  0.03  per  cent  Ca.) 


148  CHEMICAL  REAGENTS 


Heavy  Metals.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should  show  no 
change  with  hydrogen  sulphide  water;  and  after  adding  a  few  drops  of  ammonium 
sulphide  solution,  neither  a  green  or  brown  color  nor  a  precipitate  should  appear. 
(Indicating  none  present.) 

Chlorides  and  Sulphates.  —  The  solution  of  1  gm.  of  potassium  and  sodium 
tartrate  in  10  c.c.  of  water,  with  5  c.c.  of  nitric  acid  added,  should  not  be  affected 
by  silver  nitrate  and  barium  nitrate  solutions.  (Indicating  less  than  0.0005 
per  cent  Cl  and  less  than  0.175  per  cent  SO3.) 

Ammonium  Compounds.  —  On  heating  the  solution  of  1  gm.  of  potassium 
and  sodium  tartrate  in  10  c.c.  of  water  with  10  c.c.  of  sodium  hydroxide  solu- 
tion (sp.gr.  1.3),  no  vapors  of  ammonia  should  be  given  o'ff  (to  be  ascertained 
by  means  of  moist  litmus  paper).  (Indicating  less  than  0.0045  per  cent  NH3.) 

PUMICE  STONE,   PLATINIZED 

Fragments  of  pumice  stone  impregnated  with  platinum  chlo- 
ride solution  and  subsequently  ignited.  The  preparation  is  used 
as  a  catalysing  agent. 

Dark-gray,  irregular  pieces  about  the  size  of  peas,  possessing  a 
dull  metallic  luster. 

PYROGALLOL 

(Acid  Pyrogallic) 

C6H3(OH)3.     Mol.  Wt.  126.05 

White,  shining  needles  or  scales,  melting  at  131°  C.  Pyrogallol 
is  soluble  in  1.7  parts  of  wafer,  in  1  part  of  alcohol,  and  in  1.5  parts 
of  ether;  it  is  difficultly  soluble  in  benzene,  chloroform,  and  carbon 
disulphide.  The  aqueous  solution  is  slightly  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Inorganic  Matter.  —  1  gm.  of  pyrogallpl,  on  being  heated,  should  volatilize 
and  leave  no  weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

Gallic  Acid.  —  2<  gm.  of  pyrogallol  must  completely  dissolve  in  5  c.c.  of 
ether  (sp.gr.  0.72),  and  afford  a  clear  solution.  (Indicating  less  than  1  per  cent 
gallic  acid,  C7H6O6.i 

QUARTZ  SAND 

This  sand  is  prepared  for  laboratory  use  by  washing  and  subse- 
quently igniting  it. 

TESTS   OF  PURITY 

Substances  Soluble  in  Hydrochloric  Acid.  —  Digest  20  gm.  of  quartz  sand 
with  a  mixture  of  20  c.c.  of  hydrochloric  acid  and  100  c.c.  of  water  for  about 
four  hours  on  the  water-bath  with  frequent  shaking,  filter,  evaporate  50  c.c. 
of  the  filtrate  to  dryness  and  ignite  the  residue.  The  weight  of  the  ignited 
residue  should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.03  per  cent.) 

Chlorides.  —  On  shaking  1  gm.  of  quartz  sand  with  20  c.c.  of  water,  filtering, 


RESORCINOL  149 


and  adding  silver  nitrate  solution  to  the  filtrate,  at  most  a  slight  opalescence 
should  appear,     (Indicating  less  than  0.002  per  cent  Cl.) 

Volatile  Substances.  —  On  igniting  5  gm.  of  quartz  sand  the  loss  in  weight 
should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.02  per  cent.) 

RESORCINOL 

(Resorcin) 
C6H4(OH)2.    Mol.  Wt.  110.05 

Colorless  crystals,  having  a  scarcely  perceptible  but  peculiar  odor, 
soluble  in  about  1  part  of  water,  or  alcohol,  easily  soluble  in  ether 
and  in  glycerin;  difficultly  soluble  in  chloroform  and  in  carbon 
disulphide.  Resorcinol  volatilizes  on  being  heated,  and  melts  at 
110°  to  111°  C.  The  aqueous  solution  is  acid  to  litmus  paper. 
TESTS  OF  PURITY 

Non- Volatile  Matter.  —  1  gm.  of  resorcinol,  on  being  heated  and  volatilized, 
should  leave  no  weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

Diresorcin  and  Phenol.  —  1  gm.  of  resorcinol  should  yield  a  perfectly  clear 
solution  with  20  c.c.  of  water;  and  the  solution  on  being  warmed  should  not 
have  a  phenolic  odor.  (Indicating  none  present.) 

Free  Acids  (e.g.,  Salicylic  Acid).  —  On  dissolving  1  gm.  of  resorcinol  in  10 
c.c.  of  85  per  cent  alcohol,  and  adding  1  drop  of  lacmoid  solution,  a  wine-red 
liquid  is  obtained,  which/ on  the*  addition  of  1  drop  of  decinormal  solution  of 
potassium  hydroxide,  should  assume  a  blue  color.  (Indicating  none  present. 

SEA  SAND 

This  sand  is  prepared  for  laboratory  use  by  treatment  with  acid 
and  subsequent  ignition. 

TESTS   OF  PURITY 

Substances  Soluble  in  Hydrochloric  Acid.  —  Digest  20  gm.  of  sea-sand  with 
a  mixture  of  20  c.c.  of  hydrochloric  acid  and  100  c.c.  of  water  for  about  four 
hours  on  the  water-bath  with  frequent  shaking,  filter,  evaporate  50  c.c.  of  the 
filtrate,  and  ignite  the  residue.  The  weight  of  the  ignited  residue  should  not 
exceed  0.01  gm.  (Indic.ating  not  more  than  0.3  per  cent.) 

Chloride.  —  On  shaking  1  gm.  of  sea  sand  with  20  c.c.  of  water,  filtering, 
and  adding  silver  nitrate  solution  to  the  filtrate,  at  most  a  slight  opalescence 
should  appear.  (Indicating  less  than  0.002  per  cent  Cl.) 

Volatile  Substances.  —  On  igniting  5  gm.  of  sea  sand  the  loss  in  weight 
should  not  exceed  0.001  gm.  (Indicating  not  more  than  0.02  per  cent.) 

SILVER 

Ag.    Atomic  Wt.  107.88 

A  white,  shining  metal,  almost  entirely  insoluble  in  hydrochloric 
acid  and  in  cold  dilute  sulphuric  acid;  soluble  in  nitric  and  in  hot 
concentrated  sulphuric  acids. 


150  CHEMICAL  REAGENTS 


TESTS  OF  PURITY 

Foreign  Metals.  —  Dissolve  2  gm.  of  silver  in  10  c.c.  of  nitric  acid.  The 
solution  should  be  colorless  and  there  should  be  no  insoluble  residue.  Upon 
dilution  with  water  no  turbidity  should  occur.  Precipitate  the  silver  by  adding 
hydrochloric  acid  to  the  boiling  solution,  filter,  and  evaporate  the  filtrate  to 
dryness.  No  weighable  residue  should  remain.  (Indicating  less  than  0.025 
per  cent.) 

Quantitative  Determination.  —  0.2  to  0.3  gm.  of  silver  are  dissolved  in 
10  c.c.  of  nitric  acid  with  the  aid  of  heat,  continuing  the  heating  until  the  red 
fumes  have  disappeared.  After  diluting  with  100  a.c.  of  water  and  adding  5 
c.c.  of  a  cold,  saturated  solution  of  ammonium  ferric  sulphate,  titrate  with 
decinormal  ammonium  sulphocyanate  solution. 

1  c.c.  of  decinormal  NH4SCN=  0.010788  gm.  of  Ag,  log.  03294, 


SILVER  NITRATE 

AgNO3.     Mol.  Wt.  169.89 

Colorless,  lustrous  crystals  or  white  sticks,  exhibiting  a  stellate, 
crystalline  fracture,  and  yielding  a  clear,  colorless  solution  with  0.6 
part  of  water,  and  with  14  parts  of  alcohol  (about  85  per  cent  by 
weight).  The  aqueous  solution  should  be  neutral  to  litmus  paper. 
The  preparation  contains  100  per  cent  of  AgNOa- 

TESTS   OF  PURITY 

Chlorides.  —  Dissolve  5  gm.  of  silver  nitrate  in  5  c.c.  of  water,  and  allow  the 
solution  to  run  into  100  c.c.  of  water.  No  turbidity  or  opalescence  should  appear. 
(Indicating  less  than  0.002  per  cent  Cl). 

Potassium  Nitrate.  —  Dissolve  0.5  gm.  of  silver  nitrate  in  0.5  c.c.  of  water, 
mix  the  solution  with  20  c.c.  of  absolute  alcohol,  and  shake  for  a  few  minutes. 
No  turbidity  or  precipitate  should  form. 

Salts  of  Copper,  Bismuth,  and  Lead.  —  Dissolve  1  gm.  of  silver  nitrate  in 
5  c.c.  of  water,  and  add  to  the  solution  1C  c.c.  of  ammonia  water.  The  liquid 
should  remain  clear  and  colorless.  (Indicating  less  than  0.002  per  cent  Cu,  less 
than  0.02  per  cent  Bi,  or  less  than  0.3  per  cent  Pb.) 

Substances  Not  Precipitated  by  Hydrochloric  Acid.  —  Dissolve  2  gm.  of 
silver  nitrate  in  50  c.c.  of  water,  heat  the  solution  to  boiling,  and  add  3  c.c.  of 
hydrochloric  acid.  After  the  precipitate  has  settled,  filter,  and  evaporate  the 
filtrate  to  dryness.  No  weighable  residue  should  remain.  (Indicating  less  than 
0.025  per  cent.) 

Quantitative  Determination.  —  1  gm.  of  silver  nitrate  is  dissolved  in  water, 
and  diluted  to  100  c.c.  20  c.c. "of  this  solution  are  mixed  with  100  c.c.  of  water, 
10  c.c.  of  nitric  acid,  and  5  c.c.  of  a  cold,  saturated  solution  of  ammonium  ferric 
sulphate,  and  then  titrated  with  decinormal  ammonium  sulphocyanate  solution. 

1  c.c.  of  decinormal  NH4SCN=  0.016989  gm.  of  AgN03,  log.  23016. 


SILVER  NITRITE  151 

SILVER  NITRITE 

AgNO2.     Mol.  Wt.  153.89 

Small,  yellowish,  acicular  crystals,  slowly  soluble  in  about  300 
parts  of  cold  water.  Silver  nitrite  is  more  readily  soluble  in  hot 
water,  but  suffers  partial  decomposition  therein. 

TESTS  OF  PURITY 

Substances  Not  Precipitated  by  Hydrochloric  Acid.  —  Dissolve  2  gm.  of 
silver  nitrite,  with  heat,  in  100  c.c.  of  water,  with  the  aid  of  2  c.c.  of  nitric  acid, 
heat  the  solution  to  boiling,  and  add  3  c.c.  of  hydrochloric  acid.  After  the  pre- 
cipitate has  settled,  filter,'  and  evaporate  the  filtrate  to  dryness.  No  weighable 
residue  should  remain.  (Indicating  less  than  0.025  per  cent.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  silver  nitrite  in  cold  water, 
and  dilute  to  500  c.c.  Make  a  mixture  containing  10  c.c.  of  decinormal  potas- 
sium permanganate  solution,  10  c.c.  of  diluted  sulphuric  acid,  and  300  c.c.  of 
water,  heat  it  to  40  to  50°  C.,  and  run  the  nitrite  solution  into  it  until  the  pink 
color  just  disappears.  Care  must  be  taken  towards  the  end  to  introduce  the 
nitrite  solution  very  slowly,  because  the  change  from  pink  to  colorless  always 
requires  some  time. 

1  c.c.  of  decinormal  KMnO4  =  0.0076945  gm.  of  AgNO2,  log.  88618. 

SODIUM 

Na.    Atomic  Wt.  23.00. 

The  metal,  when  freshly  cut,  has  a  silver-white  surface,  which 
rapidly  becomes  dull  on  exposure  to  air  and  becomes  covered  with 
crusts  of  sodium  oxide,  sodium  hydroxide,  and  sodium  carbonate. 
At  ordinary  temperatures,  sodium  has  the  consistency  of  wax,  but 
at  low  temperatures  it  is  brittle. 

TESTS  OF  PURITY 

Nitrogen  Compounds  and  Foreign  Metals.  —  (a)  1  gm.  of  sodium  is  freed 
from  adhering  petroleum  by  wiping  with  pieces  of  filtering  paper,  then  cut  into 
small  pieces,  and  thrown  upon  20  c.c.  of  cold  water.  The  solution  of  sodium 
hydroxide  so  obtained  should  not  have  the  odor  of  ammonia  on  warming  (indi- 
cating less  than  0.07  per  cent  N),  and  should  appear  unchanged  upon  adding 
ammonium  sulphide  solution.  (Indicating  no  heavy  metals  present.) 

(6)  The  solution  prepared  from  1  gm.  of  sodium  and  20  c.c.  of  water  should 
be  unchanged  in  appearance  on  the  addition  of  10  c.c.  of  hydrochloric  acid, 
followed  by  hydrogen  sulphide  water.  (Indicating  no  heavy  metals  present.) 

SODIUM  ACETATE 
NaC2H3O2+3H2O.     Mol.  Wt.  136.07 

Colorless,  transparent  crystals,  efflorescent  in  warm  air,  soluble 
in  about  1  part  of  water,  in  29  parts  of  cold,  and  1  part  of  boiling, 
alcohol  (about  85  per  cent  by  weight). 


152  CHEMICAL  REAGENTS 

The  solution  of  1  gm.  of  sodium  acetate  in  1  c.c.  of  water  is 
alkaline  to  litmus  paper.  It  should,  however,  not  be  reddened,  or 
only  very  slightly,  by  phenolphthalein  solution;  and  any  red  color 
should  disappear  on  adding  1  drop  of  decinormal  hydrochloric 
acid  solution. 

TESTS   OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  acetate  in  20  c.c.  of  water 
should  appear  unchanged  on  adding  1  c.c.  of  nitric  acid  followed  by  silver  nitrate 
solution.  (Indicating  less  than  0.0005  per  cent  Cl.) 

Sulphates.  —  20  c.c.  of  the  1  : 20  aqueous  solution  should  not  be  rendered 
turbid  by  barium  chloride  solution.  (Indicating  less  than  0.01  per  cent  SO3.) 

Heavy  Metals  and  Calcium.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should 
not  be  affected  by  hydrogen  sulphide  water  (indicating  no  heavy  metals  present), 
or  by  ammonium  oxalate  solution.  (Indicating  less  than  0.02  per  cent  Ca.) 

Iron.  —  The  solution  of  1  gm.  of  sodium  acetate  in  20  c.c.  of  water  should 
not  be  reddened  on  adding  1  c.c.  of  hydrochloric  acid,  followed  by  potassium 
sulphocyanate  solution,  (Indicating  less  than  0.0008  per  cent  Fe.) 

SODIUM  AMALGAM 

Gray  pieces,  the  size  of  peas,  containing  2  per  cent  of  metallic 

sodium. 

TEST   OF  STRENGTH 

Quantitative  Determination  of  Sodium.  —  Introduce  10  gm.  of  sodium 
amalgam  into  100  c.c.  of  water,  and  allow  the  mixture  to  stand  with  repeated 
shaking  until  the  evolution  of  hydrogen  entirely  ceases.  Then  titrate  with 
normal  solution  of  hydrochloric  acid,  using  methyl  orange  as  the  indicator. 

1  c.c.  of  normal  HC1  =  0.0230  gm.  of  Na,  log.  36173. 

SODIUM  BICARBONATE 

NaHCO3.     Mol.  Wt.  84.01 

White,  crystalline  crusts,  or  crystalline  powder,  soluble  in  12 
parts  of  water,  but  insoluble  in  alcohol.  The  aqueous  solution  is 
faintly  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Sulphates.  —  Dissolve  2  gm.  of  sodium  bicarbonate  in  30  c.c.  of  water, 
add  10  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  add  barium  chloride  solution. 
No  precipitate  of  barium  sulphate  should  form  within  fifteen  hours.  (Indicating 
less  than  0.0125  per  cent  SO3.) 

Silicates.  —  Dissolve  5  gm.  of  sodium  bicarbonate  in  15  c.c.  of  water  and 
25  c.c.  of  hydrochloric  acid  in  a  platinum  dish.  Evaporate  the  solution  on  the 
water-bath,  dry  the  residue  for  half  an  hour  at  120°  C.,  and  then  dissolve  it  in 
3  c.c.  of  hydrochloric  acid  and  25  c.c.  of  water.  The  solution  should  be  perfect!" 
clear.  (Indicating  none  present.) 


SODIUM  BISULPHATE  153 


Chlorides  and  Thiosulphates.  —  On  adding  to  the  solution  of  1  gm.  of  sodium 
bicarbonate  in  47  c.c.  of  water,  3  c.c.  of  nitric  acid,  the  solution  should  be  clear; 
and  on  adding  silver  nitrate  solution,  at  most  a  faint  opalescence  should  develop 
within  ten  minutes.  (Indicating  less  than  0.001  per  cent  Cl,  and  less  than  0.0065 
per  cent  Na2S2O3.) 

Phosphates.  —  Dissolve  2  gm.  of  sodium  bicarbonate  in  20  c.c.  of  water, 
add  20  c.c.  of  nitric  acid  and  10  c.c.  of  ammonium  molybdate  solution.  On 
heating  to  30°  to  40°  C.,  no  yellow  precipitate  should  form  within  two  hours. 
(Indicating  less  than  0.033  per  cent  P2O5.) 

Heavy  Metals.  —  (a)  The  solution  of  3  gm.  of  sodium  bicarbonate  in  40 
c.c.  of  water  and  8  c.c.  of  hydrochloric  acid  should  remain  unchanged  on  the 
addition  of  hydrogen  sulphide  water;  on  adding  to  the  liquid  5  c.c.  of  ammonia 
water  and  a  few  drops  of  ammonium  sulphide  solution,  no  precipitate  should 
form,  nor  should  a  green  or  brown  color  develop.  (Indicating  none  present.) 

(6)  The  solution  of  1  gm.  of  sodium  bicarbonate  in  15  c.c.  of  water  and  2 
c.c.  of  hydrochloric  acid  after  adding  a  few  drops  of  nitric  acid  and  boiling  should 
not  be  more  than  slightly  reddened  on  the  addition  of  potassium  sulphocyanate 
solution.  (Indicating  less  than  0.0015  per  cent  Fe.) 

Potassium.  —  The  yellow  color  imparted  by  sodium  bicarbonate  to  the 
flame,  when  observed  through  cobalt  glass,  should  have  at  most  a  transient 
violet  tinge.  (Indicating  less  than  0.4  per  cent  K.) 

Monocarbonate  (Neutral  Sodium  Carbonate.)  —  (a)  A  solution  of  1  gm.  of 
sodium  bicarbonate  in  20  c.c.  of  water,  prepared  at  a  temperature  not  above  15° 
C.,  without  excessive  shaking,  should  not  be  more  than  slightly  reddened  on  the 
addition  of  3  drops  of  phenolphthalein  solution.  (Indicating  at  most  a  trace.) 

(6)  If  1  gm.  of  the  sodium  bicirbonate  is  dried  over  sulphuric  acid  before 
weighing,  and  is  them  ignited,  it  should  le  .ve  u  residue  weighi.ig  not  more  than 
0.638  gm. 

Ammonium  Compounds.  —  On  heating  1  gm.  of  sodium  bicarbonate  in  a 
test-tube,  no  vapors  of  ammonia  should  be  evolved  (to  be  ascertained  by  moist- 
ened turmeric  paper).  (Indicating  less  than  0.0032  per  cent  NH3.) 

Sulpho-yanates. —  The  solution  of  1  gm.  of  sodium  bicarbonate  in  3  c.c. 
of  nitric  acid  and  47  c.c.  of  water  should  not  be  reddened  on  the  addition  of  1 
drop  of  ferric  chloride  solution.  (Indicating  less  than  0.1  per  cent  CNS.) 

Quantitative  Determination.  —  On  titrating  1  gm.  of  sodium  bicarbonate 
with  normal  solution  of  hydrochloric  acid,  using  methyl  orange  as  the  indicator, 
11.9  c.c.  of  the  acid  should  be  required. 

1  c.c.  of  normal  HC1  =  0.08401  gm.  of  NaHCO3,  log.  92433. 

SODIUM   BISULPHATE 

(Sodium  Acid  Sulphate) 

NaHSO4+H2O.    Mol.  Wt.  138.09 

Colorless  crystals,  easily  soluble  in  water.  The  aqueous  solution 
is  strongly  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Heavy  Metals.  —  The  solution  of  1  gm.  of  sodium  bisulphate  in  20  c.c. 
of  water  should  not  be  affected  by  hydrogen  sulphide  water;  nor  should  a  pre- 
cipitate 01  a  green  or  brown  color  be  produced  on  making  it  alkaline  with  ammonia 
water,  and  then  adding  a  few  drops  of  ammonium  sulphide  solution.  (Indi- 
cating none  present.) 


154  CHEMICAL  REAGENTS 


Chlorides.  —  The  1  :  20  aqueous  solution  should  not  be  rendered  more 
than  slightly  opalescent  on  adding  silver  nitrate  solution.  (Indicating  less  than 
0.002  per  cent  Cl). 

Arsenic.  —  The  mixture  of  1  gm.  of  powdered  sodium  bisulphate  with  3  c.c. 
of  stannous  chloride  solution  should  not  acquire  a  darker  color  within  one  hour. 
(Indicating  less  than  0.0015  per  cent  As.) 

Potassium.  —  The  yellow-colored  flame  produced  by  sodium  bisulphate, 
when  observed  through  cobalt  glass,  should  exhibit  only  a  transient  violet  color. 
(Indicating  less  than  0.4  per  cent  K.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  bisulphate  in  50 
c.c.  of  water,  and  titrate  with  normal  potassium  hydroxide  solution,  using 
methyl  orange  as  the  indicator. 

1  c.c.  of  normal  KOH  =0.13809  gm,  of  NaHS04+H20,  log,  14016. 


SODIUM  BISULPHITE 
(Sodium  Acid  Sulphite) 
NaHSO3.    Mol.  Wt.  104.08. 

A  white  powder,  having  an  odor  of  sulphurous  acid,  and  soluble 
in  4  parts  of  water.  The  aqueous  solution  is  acid  to  litmus  paper. 

TESTS   OF  PURITY 

Chlorides.  —  Dissolve  1  gm.  of  sodium  bisulphite  in  10  c.c.  of  water,  add 
10  c.c.  of  perhydrol  (hydrogen  peroxide,  30  per  cent)  and  a  solution  of  potassium 
hydroxide  (purest)  until  the  solution  has  an  alkaline  reaction.  Evaporate  the 
solution  on  the  water-bath,  dissolve  the  residue  in  20  c.c.  of  water,  acidulate 
with  nitric  acid,  and  add  silver  nitrate  solution.  At  most  a  slight  opalescence 
should  appear.  (Indicating  less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  Dissolve  2  gm.  of  sodium  bisulphite  in  10  c.c.  of  water, 
add  20  c.c.  of  hydrochloric  acid,  and  evaporate  on  the  water-bath.  Dissolve 
the  residue  in  20  c.c.  of  water  and  add  to  the  solution  hydrogen  sulphide  water 
no  change  should  occur,  and  no  precipitate  should  form  on  the  further  addition 
of  ammonia  water  and  ammonium  sulphide  solution.  (Indicating  none  present.) 

Arsenic.  —  Add  5  gm.  of  sodium  bisulphite  in  small  portions  to  25  c.c.  of 
nitric  acid  (sp.gr.  1.3),  and  afterwards  add  5  c.c.  of  concentrated  sulphuric  acid 
and  evaporate  the  mixture,  first  as  far  as  possible  on  the  water-bath,  and  finally 
on  a  sand-bath  until  fumes  of  sulphuric  acid  begin  to  be  evolved.  After  cooling, 
dissolve  the  residue  in  50  c.c.  of  water. 

Set  in  operation  a  Marsh  apparatus  by  means  of  20  gm.  of  arsenic-free  zinc 
and  diluted  sulphuric  acid  (1  :  5),  and  add  the  solution,  prepared  as  above,  in 
small  portions  to  the  generating  flask  of  the  apparatus.  No  deposit  of  arsenic 
should  be  visible  in  the  reduction  tube  within  one  hour.  (Indicating  less  than 
0.0002  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  bisulphite  in 
thoroughly  boiled  water,  and  dilute  to  100  c.c.  Run  this  solution  from  a  burette 
into  a  mixture  of  30  c.c.  of  decinormal  iodine  solution  and  5  c.c.  of  hydrochloric 
acid,  with  constant  shaking,  until  complete  decoloration  ensues. 

1  c.c.  of  decinormal  1=0.005204  gm.  of  NaHSO3,  log.  71634. 


SODIUM  BORATE  155 


SODIUM  BORATE,  CRYSTALS 

(Borax;  Sodium  Tetraborate ;  Sodium  Biborate) 
Na2B4O7+ioH2O.    Mol.  Wt.  382.16 

Hard,  white  crystals,  or  crystalline  pieces,  soluble  in  about  25 
parts  of  cold,  and  in  0.5  part  of  boiling  water,  freely  soluble  in  glycerin, 
but  almost  insoluble  in  alcohol.  When  borax  is  heated,  it  swells 
up,  the  water  of  crystallization  being  expelled,  and  at  a  red  heat 
the  anhydrous  borax  fuses  to  a  transparent,  colorless  mass. 

The  aqueous  solution  is  alkaline  to  litmus  paper,  and  when  acid- 
ulated with  hydrochloric  acid  it  colors  turmeric  paper  brown.  The 
brown  color  becomes  particularly  evident  as  the  paper  dries,  and 
when  moistened  with  ammonia  water  the  color  becomes  greenish- 
black. 

I 

SODIUM  BORATE 

TESTS   OF  PURITY 

Carbonates  and  Sulphates.  —  The  solution  of  1  gm.  of  borax  in  20  c.c. 
of  water  should  not  effervesce  on  the  addition  of  5  c.c.  of  hydrochloric  acid 
(indicating  less  than  2  per  cent  CO2),  and  should  not  be  affected  by  the  subse- 
quent addition  of  barium  chloride  solution.  (Indicating  less  than  0.0875  per 
cent  SO2). 

Chlorides.  —  On  adding  to  20  c.c.  of  the  1  : 20  aqueous  solution  3  c.c.  of 
nitric  acid  followed  by  silver  nitrate  solution,  at  most  a  slight  opalescent  tur- 
bidity should  develop.  (Indicating  less  than  0.002  per  cent  Cl.) 

Quantitative  Determination.*  —  Dissolve  1  gm.  of  borax  in  50  c.c.  of  water, 
add  1  drop  of  methyl  orange  solution,  and  titrate  with  fifth-normal  hydrochloric 
acid  solution. 

1  c.c.  of   fifth-normal  HC1  =  0.038216  gm.  of  Na2B407+10H2O,  log.  58224. 

II 

SODIUM  BORATE,  PUREST,   CRYSTALS 
TESTS   OF  PURITY 

Content  of  Water,  f —  1  gm.  of  borax,  on  ignition,  should  yield  a  residue 
weighing  0.529  gm.  (52.9  per  cent.) 


*  Compare  method  of  Schwartz  as  given  in  Sutton,  Volumet.  Anal.,  10  ed., 
p.  95  (1911). 

t  Besides  this  prismatic  borax  containing  10  molecules  of  water  of  crystalliza- 
tion, there  is  another  borax  containing  5  molecules  of  water  of  crystallization, 
crystallizing  in  octahedra. 


156  CHEMICAL  REAGENTS 


Carbonates  and  Sulphates.  —  The  solution  of  1  gm,  of  borax  in  20  c.c.  of 
water  should  not  effervesce  on  adding  5  c.c.  of  hydrochloric  acid,  (indicating 
less  than  2  per  cent  CO  2),  nor  should  it  become  turbid  on  the  subsequent 
addition  of  barium  chloride  solution.  (Indicating  less  than  0.0875  per  cent  SOs.) 

Chlorides.  —  On  adding  to  20  c.c.  of  the  1  :  20  aqueous  solution  3  c.c.  of 
nitric  acid,  followed  by  silver  nitrate  solution,  no  change  should  appear.  (Indicat- 
ing less  than  0.0005  per  cent  Cl.) 

Calcium.  —  The  solution  of  1  gm.  of  borax  in  20  c.c.  of  water  should  not  be 
rendered  turbid  by  ammonium  oxalate  solution.  (Indicating  less  than  0.02  per 
cent  Ca.) 

Iron  and  Other  Metals. — (a)  The  solution  of  1  gm.  of  borax  in  20  c.c.  of  water 
should  not  be  reddened  on  the  addition  of  2  c.c.  of  hydrochloric  acid,  followed 
by  potassium  sulphocyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

(6)  The  1  :  20  aqueous  solution,  acidulated  with  2  c.c.  of  hydrochloric  acid, 
should  remain  unchanged  on  the  addition  of  hydrogen  sulphide  water.  (Indi- 
cating no  other  heavy  metals  present.) 

Quantitative  Determination.  —  The  determination  is  carried  out  as  detailed 
under  Sodium  Borate. 

SODIUM   BORATE,  PUREST,   CALCINED 

A  white,  spongy  mass,  or  white  powder,  containing  at  least  75 
per  cent  of  Na2B40y  (anhydrous). 

TESTS   OF   PURITY 

The  tests  to  be  made  are  those  given  under  Sodium  Borate,  Purest,  Crystals. 
But  for  each  gram  of  crystallized  borax  use  0.7  gm.  of  the  calcined. 

Quantitative  Determination.*  —  Dissolve  1  gm.  of  calcined  borax  in  50  c.c. 
of  water,  add  1  drop  of  methyl  orange  solution,  and  titrate  with  fifth-normal 
hydrochloric  acid  solution.  At  least  37.2  c.c.  of  the  acid  should  be  necessary 
to  produce  the  end-point. 

1  c.c.  of  fifth-normal  HC1  =  0.0202  gm.  of  Na2B4O7,  log.     30535. 

SODIUM  BORATE,  PUREST,  FUSED 

(Borax  Glass;  Anhydrous  Borax) 
Na2B4O7.     Mol.  Wt.  202.0 

Colorless,  vitreous  pieces,  which  take  up  moisture  from  the  air, 
and  in  consequence  become  opaque. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Sodium  Borate,  Purest,  Crystals. 
But  for  each  gram  of  the  crystallized  borax  use  0.5  gm.  of  the  fused.  Pulverize 
the  pieces  in  an  agate  mortar. 

Quantitative  Determination.  —  This  is  carried  out  as  described  under 
Sodium  Borate,  Purest,  Calcined. 


Compare  methods  given  by  Sutton,  Volumet.  Anal.,  10  ed.,  p.  95  (1911). 


SODIUM  BROMATE  157 

SODIUM  BROMATE 

NaBrO3    Mol.  Wt.  150.92 

Lustrous  crystals,  or  crystalline  powder,  soluble  in  3  parts  of 
cold,  and  in  about  1.5  parts  of  boiling,  water. 

TESTS   OF  PURITY 

Bromides.  —  On  dissolving  2  gm.  of  sodium  bromate  in  20  c.c.  of  water, 
and  adding  diluted  sulphuric  acid,  the  solution  should  not  immediately  acquire 
a  yellow  color.  (Indicating  less  than  0.03  per  cent  Br.) 

Quantitative  Determination.  —  Dissolve  0.10  to  0.15  gm.  of  sodium  bromate 
in  20  c.c.  of  water,  add  3  gm.  of  potassium  iodide  and  5  c.c.  of  hydrochloric 
acid,  and  titrate  the  liberated  iodine  with  decinormal  sodium  thiosulphate 
solution. 

1  c.c.  of  decinormal  Na2S2O3=  0.0025153  gm.  of  NaBrO3,  log.  40059. 

SODIUM     CARBONATE 


SODIUM   CARBONATE,  CRYSTALS 
Na2CO3+ioH2O.    Mol.  Wt.  286.16 

Colorless,  transparent  crystals,  efflorescent  in  the  air,  soluble  in 
1.6  parts  of  cold,  and  0.2  part  of  boiling,  water.  The  aqueous  solution 
is  strongly  alkaline  to  litmus  paper.  •  Sodium  carbonate  is  insoluble 
in  absolute  alcohol.  The  crystallized  sodium  carbonate  contains 
37  per  cent  of  the  anhydrous  salt,  Na2COs. 

TESTS   OF  PURITY 

Substances  Insoluble  in  Water.  —  20  gm.  of  sodium  carbonate  should  com- 
pletely dissolve  in  80  c.c.  of  water,  yielding  a  perfectly  colorless  solution.  (Indi- 
cating none  present.) 

Sodium  Hydroxide.  —  In  a  graduated  flask  of  100  c.c.  capacity,  dissolve 
3  gm.  of  crystallized  sodium  carbonate  in  50  c.c.  of  water,  add  to  the  solution 
6  gm.  of  crystallized  barium  chloride  dissolved  in  30  c.c.  of  water,  and  then  fill 
with  water  up  to  the  mark.  After  thoroughly  shaking,  filter,  and  to  50  c.c.  of 
the  filtrate  add  some  phenolphthalein  solution.  The  liquid  should  not  acquire 
a  red  color.  Use  boiled  water  throughout.  (Indicating  less  than  0.1  per  cent 
NaOH.) 

Sulphates.  —  On  boiling  a  solution  of  10  gm.  of  sodium  carbonate  in  50  c.c. 
of  water  and  10  c.c.  of  hydrochloric  acrd,  for  a  few  minutes,  and  then  adding 
barium  chloride  solution,  no  precipitate  of  barium  sulphate  should  form  within 
fifteen  hours.  (Indicating  less  than  0.00125  per  cent  SO3.) 

Chlorides.  —  The  solution  of  5  gm.  of  sodium  carbonate  in  50  c.c.  of  water 
and  10  c.c.  of  nitric  acid  should  not  be  affected  by  silver  nitrate  solution.  (Indi- 
cating less  than  0.0001  per  cent  Cl.) 

Silicates.  —  Dissolve  20  gm.  of  crystallized  sodium  carbonate  in  30  c.c. 
of  hydrochloric  acid  in  a  platinum  dish,  and  evaporate  the  solution  on  the  water- 


158  CHEMICAL  REAGENTS 


bath  to  dryness.  Dry  the  residue  half  an  hour  at  120°  C.,  and  then  dissolve 
it  in  3  c.c.  of  hydrochloric  acid  and  50  c.c.  of  water.  This  solution  should  be 
peifectly  clear.  (Indicating  none  present.) 

Nitrates.  —  Dissolve  1  gm.  of  sodium  carbonate  in  10  c.c.  of  diluted  sulphuric 
acid,  and  overlay  this  liquid  on  5  c.c.  of  a  solution  of  0.5  gm.  of  diphenylamine 
in  100  c.c.  of  concentrated  sulphuric  acid  and  20  c.c.  of  water.  No  blue  color 
should  form  at  the  contact-surfaces  of  the  two  liquids.  (Indicating  less  than 
0.007  per  cent  N2O5.) 

Phosphates.  —  To  the  solution  of  20  gm.  of  sodium  carbonate  in  50  c.c. 
of  nitric  acid  add  50  c.c.  of  a  solution  of  ammonium  molybdate  in  nitric  acid. 
No  yellow  precipitate  should  form  in  the  liquid  on  standing  two  to  three  hours 
at  about  40°  C.  (Indicating  less  than  0.001  per  cent  P2O5.) 

Potassium.  —  The  yellow  color  imparted  by  sodium  carbonate  to  the  flame, 
when  observed  through  cobalt  glass,  should  at  most  have  a  transient  violet 
tinge.  (Indicating  less  than  0.4  per  cent  K.) 

Ammonium  Compounds.  —  On  adding  1  c.c.  of  Nessler's  reagent  to  a  solu- 
tion of  10  gm.  of  sodium  carbonate,  in  50  c.c.  of  water,  no  change  should  be 
observed.  (Indicating  less  than  0.0001  per  cent  NH3.) 

Calcium  and  Magnesium.  —  Dissolve  10  gm.  of  sodium  carbonate  in  10  c.c. 
of  water  and  10  c.c.  of  hydrochloric  acid,  and  add  5  c.c.  of  ammonia  water,  fol- 
lowed by  ammonium  oxalate  solution.  The  liquid  should  not  become  turbid 
(indicating  less  than  0.002  per  cent  Ca),  and  no  precipitate  should  form  on  the 
addition  of  ammonium  phosphate  solution  and  standing  for  several  hours. 
(Indicating  less  than  0.0002  per  cent  Mg.) 

Heavy  Metals.  —  (a)  The  solution  of  20  gm.  of  sodium  carbonate  in  50  c.c.  of 
water  and  20  c.c.  of  hydrochloric  acid  should  not  be  affected  by  hydrogen 
sulphide  water;  on  now  adding  to  the  solution  5  c.c.  of  ammonia  water  and  a  few 
drops  of  ammonium  sulphide  solution,  no  turbidity  or  green  color  should  develop. 
(Indicating  none  present.) 

(6)  A  solution  of  10  gm.  of  sodium  carbonate  in  25  c.c.  of  water  and  10  c.c. 
of  hydrochloric  acid  should  not  acquire  a  red  color  on  the  addition  of  potassium 
sulphocyanate  solution.  (Indicating  less  than  0.00008  per  cent  Fe.) 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  metallic  zinc  into  the  generating 
flask  of  a  Marsh  apparatus,  and  start  the  hydrogen  by  adding  dilute  sulphuric 
acid  (1  :  5).  Dissolve  30  gm.  of  sodium  carbonate  in  100  c.c.  of  dilute  sulphuric 
acid  (1  :  5),  and  introduce  the  solution  in  small  quantities  at  a  time  into  the 
Marsh  apparatus.  After  one  hour  no  deposit  of  arsenic  should  be  visible  within 
the  reduction  tube.  (Indicating  less  than  0.00003  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  3  gm.  of  sodium  carbonate  in 
50  c.c.  of  water,  and  titrate  with  normal  solution  of  hydrochloric  acid,  using 
methyl  orange  as  the  indicator. 

1  c.c.  of  normal  HC1  =  0.14308  gm.  of  Na2CO3+lOH2O,  log.  15558. 

II 

SODIUM   CARBONATE,  ANHYDROUS 

Na2CO3.    Mol.  Wt.  106.0 
A  white  powder,  containing  99  to  100  per  cent  of  Na2C03.* 


*  Sodium  carbonate,  which  is  to  be  used  as  a  standard  in  volumetric  deter- 
minations, must  first  be  heated  for  thirty  minutes  on  a  sand-bath,  or  in  an  air- 
bath,  at  270°  to  300°  C.  See  Lunge,  Z.  angew.  Chem.,  17,  231  (1904);  abst., 
J.  Chem.  Soc.,  86,  II,  289  (1904). 


SODIUM  CHLORIDE  159 


TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Sodium  Carbonate  Crystals. 
But  for  each  gram  of  crystals  use  0.35  gm.  of  the  anhydrous. 

Quantitative  Determination.  —  Dissolve  1  gm.  in  50  c.c.  of  water  and  titrate 
with  normal  solution  of  hydrochloric  acid,  using  methyl  orange  as  indicator. 
At  least  18.7  c.c.  of  the  normal  acid  should  be  required. 

1  c.c.  of  normal  HC1  =  0.0530  gm.  of  Na2CO3,  log.  72428. 


SODIUM    CHLORIDE 

NaCl.    Mol.  Wt.  58.46 

I 
SODIUM  CHLORIDE 

White,  cubical  crystals,  or  crystalline  powder,  soluble  in  2.9 
parts  of  water.  The  aqueous  solution  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Sulphates.  —  3  gm.  of  sodium  chloride  yield  a  perfectly  clear  solution  with 
20  c.c.  of  water.  On  diluting  this  solution  with  80  c.c.  of  water,  adding  1  c.c. 
of  hydrochloric  acid,  heating  to  boiling,  and  then  adding  barium  chloride 
solution,  no  precipitate  of  barium  sulphate  should  form  within  fifteen  hours. 
(Indicating  less  than  0.0066  per  cent  SO3.) 

Alkaline  Earths  and  Heavy  Metals.  —  The  solution  of  3  gm.  of  sodium 
chloride  in  50  c.c.  of  water,  heated  to  boiling,  should  not  be  affected  by  ammonium 
oxalate  solution;  nor  by  sodium  carbonate  solution;  nor  by  ammonium  sulphide 
solution.  (Indicating  no  heavy  metals,  and  less  than  0.01  per  cent  earths  as  Ca.) 

Magnesium.  —  Dissolve  3  gm.  of  sodium  chloride  in  10  c.c.  of  water,  and 
add  5  c.c.  of  ammonia  water  and  ammonium  phosphate  solution."  No  pre- 
cipitate should  form  within  three  hours.  (Indicating  less  than  0.0007  per  cent 
Mg.) 

Iodides.  —  On  adding  to  20  c.c.  of  the  1  :  20  aqueous  solution,  one  drop  of 
ferric  chloride  solution  and  some  starch  solution,  no  blue  color  should  develop. 
(Indicating  less  than  0.15  per  cent  I.) 

Potassium.  —  On  adding  5  c.c.  of  sodium  cobaltic  nitrite  solution  to  the 
solution  of  1  gm.  of  sodium  chloride  in  10  c.c.  of  water,  no  precipitate  should 
form  within  fifteen  hours.  (Indicating  less  than  0.18  per  cent  K.) 

Iron.  —  The  solution  of  3  gm.  of  sodium  chloride  in  20  c.c.  of  water  boiled 
with  a  few  drops  of  nitric  acid  should  not  acquire  a  red  color  on  the  addition 
of  potassium  sulphocyanate  solution.  (Indicating  less  than  0.0003  per  cent  Fe.) 

Ammonium.  —  The  solution  of  3  gm.  of  sodium  chloride  in  20  c.c.  of  water 
should  not  be  changed  in  appearance  on  the  addition  of  Nessler's  reagent.  (Indi- 
cating less  than  0.0003  per  cent  NH3.) 

Quantitative  Determination.  —  Dissolve  0.2  gm.  of  sodium  chloride  in  100 
c.c.  of  water,  add  a  few  drops  of  potassium  chromate  solution,  and  titrate  with 
decinormal  silver  nitrate  solution. 

1  c.c.  of  decinormal  AgN03= 0.005846  gm.  of  NaCl,  log.  76686. 


160  CHEMICAL  REAGENTS 

II 
SODIUM  CHLORIDE,  FUSED 

Colorless  or  slightly  reddish,  translucent  pieces. 
TESTS   OF  PURITY 

The  tests  and  the  quantitative  determination  as  given  under  Sodium  Chloride 
are  to  be  made. 

SODIUM     HYDROXIDE 

(Caustic  Soda;   Sodium  Hydrate) 
NaOH.     Mol.  Wl.  40.058 

Three  grades  of  sodium  hydroxide  are  used  in  the  chemical 
laboratory: 

1.  Sodium  Hydroxide,  from  Sodium. 

2.  Sodium  Hydroxide,  Pure. 

3.  Sodium  Hydroxide,  Purified. 

These  three  preparations  vary  chiefly  in  their  content  of  chloride, 
sulphate,  silicate  and  alumina. 

I 
SODIUM  HYDROXIDE,  FROM   SODIUM 

White,  very  hygroscopic  pieces  showing  a  crystalline  structure 
on  fracture.  The  preparation  contains  from  95  to  98  per  cent  of 
NaOH. 

TESTS   OF  PURITY 

Sulphates.  —  Dissolve  3  gm.  of  sodium  hydroxide  in  50  c.c.  of  water,  acidulate 
with  15  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  add  barium  chloride  solu- 
tion. No  precipitate  of  barium  sulphate  should  form  within  fifteen  hours. 
(Indicating  less  than  0.004  per  cent  SOs.) 

Chlorides.  —  Dissolve  1  gm.  of  sodium  hydroxide  in  20  c.c.  of  water,  add 
10  c.c.  of  nitric  acid  and  a  few  drops  of  silver  nitrate  solution.  At  most  a  slight 
opalescent  turbidity  should  develop.  (Indicating  less  than  0.0025  per  cent  Cl.) 

Nitrogen.  — To  2  gm.  of  sodium  hydroxide  and  a  granule  of  sodium  chloride 
dissolved  in  10  c.c.  of  diluted  sulphuric  acid  add  1  drop  of  1  :  1000  indigo  solu- 
tion and  10  c.c.  of  concentrated  sulphuric  acid.  The  blue  color  of  the  mixture 
should  not  disappear  on  agitation.  (Indicating  less  than  0.002  per  cent  N2O5.) 

Nitrogen  as  Nitrates,  Nitrites,  Ammonia,  etc.  —  Dissolve  50  gm.  of  sodium 
hydroxide  in  100  c.c.  of  water  in  a  distillation  flask,  and  add  2  gm.  of  Devarda's 
metal.  Connect  the  flask  with  a  bulb  tube,  condenser,  and  a  receiver  con- 
taining 2  to  3  c.c.  of  fifth-normal  hydrochloric  acid  solution  and  10  c.c.  of  water, 
allow  to  stand  one  to  two  hours,  and  then  distil  off  about  50  c.c.  Titrate  the 


SODIUM  HYDROXIDE  161 


distillate  with  fifth-normal  potassium  hydroxide  solution,  using  methyl  orange 
as  the  indicator.  Not  more  than  0.2  c.c.  of  the  acid  solution  should  have  been 
required  to  neutralize  the  ammonia.  (Indicating  less  than  0.00112  per  cent  N.) 

Nitrites.  —  The  solution  of  1  gm.  of  sodium  hydroxide  in  10  c.c.  of  water  and 
10  c.c.  of  diluted  sulphuric  acid  should  not  acquire  a  blue  color  on  the  addition 
of  zinc  iodide-starch  solution.  (Indicating  less  than  0.00011  per  cent  N2O3.) 

Phosphates.  —  Dissolve  5  gm.  of  sodium  hydroxide  in  50  c.c.  of  water  and 
add  35  c.c.  of  nitric  acid  and  25  c.c.  of  a  solution  of  ammonium  molybdate  in 
nitric  acid.  No  yellow  precipitate  should  form  on  standing  two  hours  at  about 
40°  C.  (Indicating  less  than  0.003  per  cent  P2O5.)  % 

Silicates.  —  Dissolve  5  gm.  of  sodium  hydroxide  in  25  c.c.  of  water  and  25 
c.c.  of  hydrochloric  acid  in  a  platinum  dish,  and  evaporate  to  dryness  on  a  water- 
bath.  Dry  the  residue  for  half  an  hour  at  120°  C.,  and  then  dissolve  it  in  10  c.c. 
of  hydrochloric  acid  and  90  c.c.  of  water.  Any  insoluble  residue  should  be 
filtered  off,  washed,  and  ignited.  Its  weight  should  not  exceed  0.001  gm.  (Indi- 
cating not  more  than  0.02  per  cent  SiO2.) 

Aluminum,  Calcium,  and  Heavy  Metals. —  Dissolve  50  gm.  of  sodium  hydroxide 
in  250  c.c.  of  water,  add  90  c.c.  of  acetic  acid  (sp.gr.  1.064),  followed  by  40  c.c. 
of  ammonia  water,  and  heat  the  liquid  on  the  water-bath  until  the  odor  of 
ammonia  has  disappeared.  Add  a  few  drops  of  ammonia  water,  and  allow  to 
stand  fifteen  hours.  Within  this  time,  no  precipitate,  or  only  a  very  slight  floc- 
culent  precipitate,  should  form.  In  the  latter  case,  the  precipitate  is  filtered 
off  and  washed.  Its  weight  upon  ignition  should  not  exceed  0.001  gm.  (Indi- 
cating not  more  than  0.00106  per  cent  Al.)  With  the  filtrate  brought  to  a  volume 
of  400  c.c.  the  following  tests  are  made: 

To  20  c.c.  diluted  with  30  c.c.  of  water,  add  ammonium  oxalate  solution.  No 
precipitate  of  calcium  oxalate  should  form  on  standing  two  hours.  (Indicating 
less  .than  0.012  per  cent  Ca.) 

To  another  20  c.c.  add  a  few  drops  of  ammonium  sulphide  solution;  no  pre- 
cipitate should  form,  nor  should  a  brown  or  green  color  appear.  (Indicating  no 
heavy  metals.) 

Quantitative  Determination  and  Determination  of  Sodium  Carbonate  Content. 
—  Titrate  the  solution  of  1  gm.  of  sodium  hydroxide  in  100  c.c.  of  water  with 
normal  hydrochloric  acid  solution  in  the  cold,  using  phenolphthalein  as  indicator. 
At  least  24.1  c.c.  of  normal  acid  solution  should  be  required  to  destroy  the  red 
color.  Now  add  1  drop  of  methyl  orange,  and  titrate  further  until  the  color 
changes  to  red.  In  the  second  titration,  at  most  0.3  c.c.  of  the  acid  solution 
should  be  used.  (Indicating  not  more  than  3.18  per  cent  of  Na2CO3.)* 

1  c.c.  of  normal  HC1  =  0.04001  gm.  of  NaOH,  log.  60217. 
t  I  c.c.  of  normal  HC1  =  0.0530  gm.  of  Na2CO3,  log.  72428. 

II 
SODIUM   HYDROXIDE,  PURE 

White,  very  hygroscopic  sticks  or  pieces,  exhibiting  a  crystalline 
fracture.  The  preparation  contains  95  to  98  per  cent  of  NaOH. 

TESTS   OF  PURITY 

Sulphates.  —  Dissolve  3  gm.  of  sodium  hydroxide  in  50  c.c.  of  water,  acidulate 
with  15  c.c.  of  hydrochloric  acid,  heat  to  boiling,  and  add  barium  chloride  solution. 

*  Regarding  the  calculation  of  the  sodium  carbonate,  see  the  note  under 
Potassium  Hydroxide,  Purest. 


162  CHEMICAL  REAGENTS 


The  liquid  should  not  have  more  than  a  slight  turbidity;  and  it  should  still  be 
transparent  when  observed  in  a  test-tube  of  2  cm.  diameter.  (Indicating  less 
than  0.02S  per  cent  SO3.) 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  hydroxide  in  20  c.c.  of  water 
and  10  c.c.  of  nitric  acid  may  be  rendered  opalescent  by  silver  nitrate  solution, 
but  should  develop  no  precipitate  at  once.  (Indicating  less  than  0.005  per  cent  Cl.) 

Nitrates  and  Nitrogen  as  Nitrates,  Nitrites,  Ammonia,  etc.  —  The  tests  are 
carried  out  as  detailed  under  Sodium  Hydroxide,  from  Sodium. 

Silicates.  —  Dissolve  5  gm.  of  sodium  hydroxide  in  25  c.c.  of  water  with  25 
c.c.  of  hydrochloric  acid  in  a  platinum  dish,  and  evaporate  to  dryness  on  the  water- 
bath.  Dry  the  residue  for  half  an  hour  at  120°  C.,  and  then  dissolve  it  in  10  c.c. 
of  hydrochloric  acid  and  90  c.c.  of  water.  Any  insoluble  residue  is  filtered  off, 
washed,  and  ignited.  Its  weight  after  ignition  should  not  exceed  0.003  gm. 
(Indicating  not  more  than  0.06  per  cent  SiOa.) 

Aluminum,  Calcium,  and  Heavy  Metals.  —  5  gm.  of  sodium  hydroxide  should 
afford  a  clear  and  colorless  solution  with  20  c.c.  of  water.  Dilute  the  solution 
.with  80  c.c.  of  water,  add  30  c.c.  of  acetic  acid  (sp.gr.  1.041)  and  10  c.c.  of 
ammonia  water,  and  heat  upon  the  water-bath  until  the  odor  of  ammonia  has 
disappeared.  After  adding  a  few  drops  of  ammonia  water  only  a  slight  precipitate 
should  form  on  standing  fifteen  hours.  The  precipitate  is  filtered  off,  washed, 
and  ignited;  its  weight  should  then  not  exceed  0.003  gm.  (indicating  not  over  0.032 
per  cent  Al.)  The  filtrate  should  not  be  affected  by  ammonium  oxalate  solu- 
tion (indicating  less  than  0.005  per  cent  Ca) ;  and  on  adding  ammonium  sulphide 
solution,  at  most  a  slight  green  color  may  appear,  in  no  case  should  a  brown 
color  or  a  precipitate  be  produced.  (Indicating  at  most  a  trace  of  heavy  metals.) 

Quantitative  Determination  and  Determination  of  Sodium  Carbonate  Con- 
tent. —  This  is  carried  out  as  described  under  Sodium  Hydroxide,  from  Sodium. 
The  amount  of  sodium  carbonate  present  should  not  exceed  4  per  cent. 

Ill 
SODIUM  HYDROXIDE,  PURIFIED 

White,  very  hygroscopic  sticks  or  pieces,  exhibiting  a  crystalline 
fracture.  The  preparation  contains  90  to  95  per  cent  of  NaOH. 

TESTS   OF  PURITY 

Nitrogen  as  Nitrates  and  Nitrites.  —  To  the  solution  of  2  gm.  of  sodium 
hydroxide  and  a  granule  of  sodium  chloride  in  10  c.c.  of  16  per  cent  sulphuric 
acid  add  jl  drop  of  1  :  1000  indigo  solution  and  then  10  c.c.  of  concentrated 
sulphuric  acid.  The  blue  color  of  the  mixture  should  not  disappear  on  agita- 
tion. (Indicating  less  than  0.002  per  cent  N2O5.) 

Aluminum,  Calcium,  and  Heavy  Metals.  —  2.5  gm.  of  sodium  hydroxide  should 
afford  a  clear  and  colorless  solution  with  10  c.c.  of  water.  Dilute  the  solution 
with  90  c.c.  of  water  and  add  15  c.c.  of  acetic  acid  (sp.gr.  1.041)  and  5  c.c.  of 
ammonia  water.  No  precipitate  should  form.  (Indicating  less  than  0.16  per 
cent  Al.)  The  solution  thus  tested  should  not  immediately  be  rendered  turbid 
on  the  addition  of  ammonium  oxalate  solution  (indicating  less  than  0.01  per 
cent  Ca) ;  and  on  adding  to  it  ammonium  sulphide  solution,  it  should  acquire 
at  most  a  slight  green  color.  (Indicating  at  most  a  trace  of  heavy  metals.) 

Quantitative  Determination  and  Determination  of  the  Sodium  Carbonate 
Content.  —  Titrate  a  solution  of  1  gm.  of  sodium  hydroxide  in  100  c.c.  of  water 
with  normal  hydrochloric  acid  solution  in  the  cold,  using  phenolphthalein  as  the 


SODIUM  HYDROXIDE  SOLUTIONS  163 


indicator.  At  least  23  c.c.  of  normal  acid  solution  should  be  required  to  discharge 
the  color.  Now  add  1  drop  of  methyl  orange,  and  titrate  further  until  the  color 
again  changes  to  red.  In  this  second  titration  at  most  0.5  c.c.  of  the  acid  solution 
should  be  necessary.  (Indicating  not  more  than  5.30  per  cent  of  Na2CO3.)* 

1  c.c.  of  normal  HC1  =  0.04001  gm.  of  NaOH,  log.  60217. 

1  c.c.  of  normal  HC1  =  0.0530  gm.  of  Na2CO3,  log.  72428. 


SODIUM    HYDROXIDE    SOLUTIONS 
(Caustic  Soda  Solutions) 

I 
SODIUM  HYDROXIDE,  SOLUTION  I— FREE  FROM  NITROGEN 

A  colorless  liquid  of  specific  gravity  1.3,  and  containing  about  27 
per  cent  of  sodium  hydroxide,  NaOH. 

TESTS   OF  PURITY 

Nitrogen  as  Nitrates,  Nitrites,  Ammonia,  etc.  —  Place  200  c.c.  of  the  sodium 
hydroxide  solution  in  a  distillation  flask,  add  2  gm.  of  Devarda's  metal,  and  con- 
nect the  flask  with  a  bulb  tube,  a  condenser,  and  a  receiver  containing  2  to  3 
c.c.  of  fifth-normal  solution  of  hydrochloric  acid  and  10  c.c.  of  water.  After  the 
mixture  has  stood  one  to  two  hours,  distil  off  about  70  c.c.  and  titrate  the  dis- 
tillate with  fifth-normal  solution  of  potassium  hydroxide,  using  methyl  orange  as 
the  indicator.  Not  more  than  0.2  c.c.  of  the  fifth-normal  hydrochloric  acid 
solution  should  have  been  neutralized  by  the  ammonia  from  the  sodium  hydroxide. 
(Indicating  not  more  than  0.0002  per  cent  N.) 


II 

SODIUM  HYDROXIDE,  SOLUTION  H— FREE  FROM 
NITROGEN 

A  colorless  liquid  of  specific  gravity  1.3  and  containing  about 
27  per  cent  of  sodium  hydroxide,  NaOH. 

TESTS  OF  PURITY 

The  test  for  nitrogen  is  to  be  made  as  described  under  Sodium  Hydroxide, 
Solution  I.  The  tests  for  Sulphates,  Chlorides,  Silicates,  Aluminum,  Calcium,  and 
Heavy  Metals  are  to  be  carried  out  as  directed  under  Sodium  Hydroxide,  Pure. 
But  for  each  gram  of  sodium  hydroxide,  use  2.9  c.c.  (3.7  gm.)  of  sodium  hydroxide, 
solution  II. 


*  Regarding  the  calculation  of  the  sodium  carbonate,  see  the  note  under 
Potassium  Hydroxide,  Purest. 


164          .  CHEMICAL  REAGENTS 

III 
SODIUM  HYDROXIPE,  SOLUTION  III.    Sp.Gr.  1.168 

A  clear,  colorless  liquid,  of  specific  gravity  1.168  to  1.172,  and 
containing  about  15  per  cent  of  sodium  hydroxide,  NaOH. 

TESTS   OF  PURITY 

The  tests  to  be  made  are  those  given  under  Sodium  Hydroxide,  Pure.  But 
tor  each  gram  of  sodium  hydroxide,  use  5.6  c.c.  (6.5  gm.)  of  sodium  hydroxide, 
solution  III. 

SODIUM    HYDROXIDE    WITH    LIME 
(Soda-Lime) 

I 
SODIUM  HYDROXIDE  WITH  LIME 

A  white,  porous  mass,  finely  or  coarsely  granulated. 
TESTS   OF  PURITY 

Excess  of  Carbonate.  —  5  gm.  of  soda-lime,  when  treated  with  dilute  sulphuric 
acid,  should  not  effervesce  strongly.  (Indicating  less  than  5  per  cent  CO2.) 

Nitrogen.  —  (a)  On  igniting  soda-lime  in  a  test-tube,  it  should  develop  no 
vapors  of  ammonia  (to  be  ascertained  by  moistened  litmus  paper.)  (Indicating 
no  ammonia-nitrogen  present.) 

(6)  To  the  solution  of  50  gm.  of  soda-lime  in  200  c.c.  of  hydrochloric  acid 
add  2  gm.  of  Devarda's  metal,  and  let  the  mixture  stand,  with  frequent  shaking, 
until  the  evolution  of  hydrogen  has  ceased.  To  the  cold  fluid  add  100  c.c.  of 
sodium  hydroxide  solution  nitrogen-free  (sp.gr.  1.3),  and  distil  off  about  100  c.c., 
collecting  the  distillate  in  a  receiver  containing  2  to  3  c.c.  of  fifth-normal  hydro- 
chloric acid  solution  and  10  c.c.  of  water.  Titrate  the  distillate  with  fifth-normal 
potassium  hydroxide  solution,  using  methyl  orange  as  the  indicator.  No  more 
than  0.2  c.c.  of  the  acid  solution  should  have  been  required  to  neutralize  the 
ammonia.  (Indicating  not  more  than  0.00112  per  cent  N.) 

II 
SODIUM  HYDROXIDE  WITH  LIME  FROM  ICELAND  SPAR 

A  white,  porous,  granular  mass. " 

TESTS  OF  PURITY 

Chlorides.  —  Dissolve  5  gm.  of  soda-lime  in  50  c.c.  of  nitric  acid,  and  dilute 
the  solution  with  100  c.c.  of  water.  The  liquid  should  acquire  at  most  a  slight 
opalescent  turbidity  on  the  addition  of  silver  nitrate  solution.  (Indicating  less 
than  0.001  per  cent  Cl.) 


,  SODIUM  INDIGOTINSULPHONATE  .      165 


Phosphates.  —  Dissolve  10  gm.  of  soda-lime  in  100  c.c.  of  nitric  acid,  and  add 
to  the  solution  25  c.c.  of  a  solution  of  ammonium  molybdate  in  nitric  acid.  No 
yellow  precipitate  should  form  within  two  to  three  hours  on  standing  at  about 
40°  C.  (Indicating  less  than  0.003  per  cent  P2O5.) 

Sulphur.  —  Thoroughly  mix  5  gm.  of  finely  powdered  soda-lime  with  2  gm.  of 
sodium  nitrate,  and  ignite  the  mixture  in  a  silver  crucible.  Dissolve  the  melt 
in  50  c.c.  of  water  with  20  c.c.  of  hydrochloric  acid,  filter,  and  to  the  filtrate  add 
barium  chloride  solution.  No  precipitate  of  barium  sulphate  should  form  within 
fifteen  hours.  (Indicating  less  than  0.0015  per  cent  S.) 

SODIUM   INDIGOTINSULPHONATE 

(Indigo  Carmine) 
Ci6H8N2O2(SO3Na)2.    Mol.  Wt.  466.22. 
A  dark  blue  powder,  soluble  in  water. 

TESTS  OF  PURITY 

Water  Content.  —  On  drying  sodium  indigotinsulphoaate  at  100°  C.,  the  loss 
in  weight  should  not  exceed  10  per  cent. 

Determination  of  Indigo.  —  Dissolve  1  gm.  of  sodium  indigotinsulphonate 
in  water  in  a  liter  graduated  flask,  add  10  c.c.  of  concentrated  sulphuric  acid  and 
fill  to  the  mark  with  water.  Dilute  100  c.c.  of  this  solution  with  600  c.c.  of  water 
and  titrate  in  a  porcelain  dish  with  decinormal  potassium  permanganate  solution. 
It  is  to  be  noted  that  the  end-point  of  the  titration  is  the  color  change  from  green 
to  light  yellow,  and  not  the  incipient  red  coloration. 

1  c.c.  of  decinormal  KMnO4  =  0.007493  gm.  of  Ci6HioN2O2  (indigotin),*  log. 
87466. 

SODIUM  NITRATE 

NaNO3.     Mol.  Wt.  85.01 

Colorless,  transparent,  rhombohedric  crystals,  soluble  in  1.2 
parts  of  water  and  in  80  parts  of  alcohol  of  85  per  cent  by  weight. 
The  aqueous  solution  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Sulphates.  —  On  dissolving  3  gm.  of  sodium  nitrate  in  60  c.c.  of  water,  and 
adding  1  c.c.  of  hydrochloric  acid  followed  by  barium  chloride  solution,  no  pre- 
cipitate of  barium  sulphate  should  form  on  standing  fifteen  hours.  (Indicating 
less  than  0.0025  per  cent  SO3.) 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  nitrate  in  20  c.c.  of  water 
acidulated  with  1  c.c.  of  nitric  acid,  should  not  be  rendered  turbid  on  the  addition 
of  silver  nitrate  solution.  (Indicating  less  than  0.0015  per  cent  Cl.) 

Chlorates  and  Perchlorates.  —  On  gently  igniting  1  gm.  of  sodium  nitrate, 
dissolving  the  residue  in  20  c.c.  of  water,  and  adding  1  c.c.  of  nitric  acid,  the 


*  O.  Miller  and  J.  Smirnoff,  Ber.,  41,  1366  (1908);  abst.',  J.  Chem.  Soc.,  94.  I, 
468  (1908). 


166  CHEMICAL  REAGENTS 


solution  should  not  be  rendered  turbid  on  adding  silver  nitrate  solution.  (Indi- 
cating less  than  0.005  per  cent  as  Cl.) 

Calcium  and  Heavy  Metals.  —  The  solution  of  3  gm.  of  sodium  nitrate  in 
50  c.c.  of  water  should  show  no  change  either  on  the  addition  of  hydrogen  sul- 
phide water  or  of  ammonia  water  and  ammonium  oxalate  solution.  (Indicating 
less  than  0.01  per  cent  Ca.)  On  adding  ammonium  sulphide  solution  neither  a 
green  or  brown  color  nor  a  precipitate  should  appear.  (Indicating  no  heavy 
metals  present.) 

Iron.  —  20  c.c.  of  the  1  :  20  aqueous  solution,  acidulated  with  1  c.c.  of  hydro- 
chloric acid,  should  not  be  reddened  on  the  addition  of  potassium  sulphocyanate 
solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Nitrites.  —  Dissolve  1  gm.  of  sodium  nitrate  in  20  c.c.  of  water,  and  add  1 
c.c.  of  diluted  sulphuric  acid  and  1  c.c.  of  a  freshly  prepared  1  :  200  colorless 
solution  of  metaphenylenediamine  hydrochloride.*  No  yellow  or  yellowish- 
brown  color  should  develop.  (Indicating  less  than  0.00055  per  cent  NaOs.) 

lodates  and  Nitrites.  —  To  5  c.c.  of  the  1  :  20  aqueous  solution  add  3  or  4 
drops  of  diluted  sulphuric  acid  and  zinc  iodide-starch  solution.  No  blue  color 
should  develop  within  one  minute.  (Indicating  less  than  0.004  per  cent  I20s, 
and  less  than  0.00005  per  cent  N2O3.) 

Potassium.  —  Dissolve  3  gm.  of  sodium  nitrate  in  6  c.c.  of  water  with  3  to 
5  drops  of  diluted  acetic  acid,  and  add  5  to  10  drops  of  solution  of  sodium-cob altic 
nitrite.  The  liquid  should  remain  clear,  and  on  standing  two  hours  at  about 
50°  C.,  no  yellow  precipitate  should  form.  (Indicating  less  than  0,33  per  cent  K.) 

SODIUM    NITRITE 

NaNO2.    Mol.  Wt.  69.01 

I 
SODIUM  NITRITE 

White,  or  slightly  yellowish,  tough  sticks,  becoming  moist  in  the 
air,  arid  soluble  in  about  2  parts  of  water.  The  aqueous  solution 
is  alkaline  to  litmus  paper.  The  preparation  contains  at  least  98 

per  cent  of  NaN02. 

TESTS   OF  PURITY 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  nitrite  in  20  c.c.  of  water  should 
not  acquire  more  than  a  slight  opalescent  turbidity  on  the  addition  of  5  c.c.  of 
nitric  acid  and  some  silver  nitrate  solution.  (Indicating  less  than  0.002  per  cent 
Cl.) 

Sulphates.  —  The  solution  of  1  gm.  of  sodium  nitrite  in  20  c.c.  of  water, 
acidulated  with  5  c.c.  of  nitric  acid,  should  not  be  rendered  turbid  on  the  addition 
of  barium  nitrate  solution.  (Indicating  less  than  0.175  per  cent  SO 3.) 

Heavy  Metals.  —  Dissolve  1  gm.  of  sodium  nitrite  and  1  gm.  of  ammonium 
chloride  in  5  c.c.  of  water,  evaporate  the  solution  to  dryness  on  the  water-bath, 
and  dissolve  the  residue  in  10  c.c.  of  water.  This  solution  should  not  be  affected 
by  hydrogen  sulphide  water;  and  after  the  addition  of  ammonia  water  and  ammo- 
nium sulphide  solution  no  green  or  brown  color  should  develop,  nor  should  a 
precipitate  form.  (Indicating  none  present.) 

*  Should  the  solution  of  metaphenylenediamine  hydrochloride  have  a  color, 
it  should  be  decolorized  before  use  by  warming  with  ignited  animal  charcoal. 


SODIUM  NITRITE  167 


Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  nitrite  in  water  and 
dilute  to  200  c.c.  Make  a  mixture  of  50  c.c.  of  decinormal  potassium  permanganate 
solution  with  300  c.c.  of  water  and  25  c.c.  of  diluted  sulphuric  acid,  and,  while 
constantly  shaking,  allow  30  c.c.  of  the  nitrite  solution  to  run  slowly  into  it. 
After  ten  minutes  add  to  the  solution  3  gm.  of  potassium  iodide,  and  titrate  the 
liberated  iodine  with  decinormal  sodium  thiosulphate  solution,  using  starch 
solution  as  the  indicator. 

1  c.c.  of  decinormal  KMn04  =  0.0034505  gm.  of  NaNO2,  log.  53788. 


II 
SODIUM  NITRITE,  FREE  FROM  POTASSIUM 

TESTS   OF  PURITY 

Potassium.  —  To  a  solution  of  5  gm.  of  crystallized  cobalt  acetate  in  12  c.c. 
of  water  add  a  solution  of  10  gm.  of  sodium  nitrite  in  20  c.c.  of  water  previously 
acidulated  with  2  c.c.  of  diluted  acetic  acid.  Dilute  the  solution  with  25  c.c. 
of  water  and  allow  it  to  stand  twenty-four  hours  at  40°  to  50°  C.  No  yellow 
precipitate  should  form  within  this  time.  (Indicating  less  than  0.03  per  cent  K.) 

Other  Tests.  —  The  other  tests  and  the  quantitative  determination  given 
under  Sodium  Nitrite  should  also  be  made,  observing  the  conditions  there 
described. 

SODIUM   NITROFERRICYANIDE 

(Sodium  Nitroprusside) 
Na2Fe(CN)&(NO)  +2H2O.     Mol.  Wt.  297.93 

Ruby-red,  transparent  crystals,  affording  a  clear  solution  with 
2.5  parts  of  water. 

TEST   OF  PURITY 

Sulphate.  —  The  solution  of  1  gm.  of  sodium  nitroprusside  in  50  c.c.  of  water 
acidulated  with  1  c.c.  of  hydrochloric  acid  should  not  be  rendered  turbid  on  adding 
barium  chloride  solution.  (Indicating  less  than  0.01  per  cent  SO3.) 

SODIUM   OXALATE 

(Sorensen's  Oxalate) 
Na2C2O4.    Mol.  Wt.  134.0 

A  white,  crystalline  powder,  soluble  in  31  parts  of  cold,  and  in 
16  parts  of  boiling,  water.  Sodium  oxalate,  which  is  to  be  used  in 
acidimetric  and  oxidimetric  determinations  as  a  standard,  is  obtained 
by  precipitation  with  alcohol,  and  drying  at  240°  C.  The  prepara- 
tion contains  100  per  cent  of 


168  CHEMICAL  REAGENTS 


TESTS  OF  PURITY 

Hygroscopic  Moisture.*  —  10  gm.  of  sodium  oxalate,  when  dried  in  a  water- 
drying-oven  for  twenty-four  hours,  should  not  lose  more  than  0.001  gm.  in  weight. 
(Indicating  not  more  than  0.01  per  cent.) 

Sodium  Carbonate,  Sodium  Binoxalate.  —  Introduce  into  a  conical  Jena  flask 
about  250  c.c.  of  water  and  10  drops  of  phenolphthalein  solution  (0.5  gm.  phenol- 
phthalein  dissolved  in  50  c.c.  of  alcohol  and  50  c.c.  of  water),  and  evaporate  to 
about  180  c.c.  while  passing  in  a  current  of  pure  air,  free  from  carbon  dioxide. 
Allow  to  cool  to  the  ordinary  temperature,  add  5  gm.  of  sodium  oxalate,  shake 
carefully,  and  maintain  the  current  of  air.  The  oxalate  slowly  dissolves.  If  the 
solution  is  red,  not  more  than  0.2  c.c.  of  decinormal  acid  solution  should  be 
required  to  render  it  colorless.  But,  if  the  solution  is  colorless,  it  must  acquire 
a  distinct  red  color  on  the  addition  of  at  most  0.1  c.c.  of  decinormal  sodium 
hydroxide  solution.  (Indicating  less  than  0.0212  per  cent,  Na2CO3  or  less  than 
0.0224  per  cent  NaHC2O4.) 

Chlorides  and  Sulphates.  —  Decompose  10  gm.  of  sodium  oxalate  by  heating 
in  a  platinum  crucible,  best  over  an  alcohol  lamp  (illuminating  gas  contains  sul- 
phur). The  carbonate  formed  is  dissolved  in  nitric  acid,  and  the  solution  filtered 
off  from  the  carbon.  On  adding  silver  nitrate  solution  to  half  of  the  nitrate, 
no  reaction  for  hydrochloric  acid  should  be  obtained  (indicating  less  than  0.0001 
per  cent  Cl);  and  in  the  other  half  no  reaction  for  sulphuric  acid  should  be 
obtained  on  adding  barium  nitrate  solution.  (Indicating  less  than  0.025  per 
cent  SO3.) 

Iron  and  Potassium.  —  Decompose  10  gm.  of  sodium  oxalate  by  igniting 
moderately  in  a  platinum  crucible,  removing  the  last  traces  of  carbon  by  cautious 
ignition  with  a  blast  lamp.  The  residue,  when  treated  with  warm  water  in  a 
platinum  dish,  should  be  completely  soluble,  and  should  leave  at  most  a  scarcely 
weighable  trace  of  undissolved  iron  oxide.  The  solution  is  filtered  if  necessary, 
and  supersaturated  with  hydrochloric  acid  as  free  from  iron  as  possible.  It  is 
then  evaporated  in  a  platinum  dish  on  the  water-bath,  and  the  residue  dried  for 
two  hours  in  the  drying  oven  at  120°  C.  The  residue  must  dissolve  clear  in 
water  and  the  solution  should  give: 

(a)  With  potassium  sulphocyanate  solution  only  a  very  faint  reaction  for 
iron  after  boiling  with  a  little  nitric  acid  (indicating  less  than  0.0003  per  cent 
Fe)  and 

(6)  With  sodium  and  cobalt  nitrite  solution,  no  reaction  for  potassium. 
(Indicating  less  than  0.06  per  cent  K.) 

Foreign  Organic  Bodies.  —  In  a  clean,  thoroughly  ignited  test-tube,  heat  1 
gm.  of  sodium  oxalate  with  10  c.c.  of  pure  concentrated  sulphuric  acid,  as  long  as 
evolution  of  gas  occurs,  at  first,  gently,  and  then  more  strongly,  until  vapors 
of  sulphuric  acid  begin  to  be  evolved.  When  cooled,  the  color  of  the  sulphuric 
acid  is  compared  with  that  of  another  portion  of  10  c.c.  of  sulphuric  acid  similarly 
treated,  _  but  without  the  addition  of  sodium  oxalate.  The  sodium  oxalate, 
treated  in  the  manner  described,  should  impart  to  the  sulphuric  acid  not  more 
than  an  exceedingly  faint  brownish  tinge.  (Indicating  at  most  a  trace  present.) 

Quantitative  Determination.  —  0.4  to  0.5  gm.  of  the  sodium  oxalate  dried 
to  constant  weight  at  100°  C.  are  cautiously  heated  in  a  covered  platinum  crucible. 
In  order  to  avoid  the  error  due  to  the  sulphur  in  illuminating  gas,  the  crucible 
is  held  in  a  sheet  of  asbestos  provided  with  a  round  hole,  or  a  Berzelius  alcohol 
lamp  is  used.  The  conversion  of  the  oxalate  into  carbonate  is  completed  in  from 
fifteen  to  thirty  minutes ;  any  carbon  present  is  then  burned  off  by  more  strongly 
heating  the  crucible  while  half  covered.  When  cold,  dissolve  the  contents  of 


*  These  tests  are  taken  from  the  original  paper  by  S.  P.  L.  Sorensen,  Z.  anal. 
Chem.,  42,  512  (1903);  abst.,  J.  Chem.  Soc.,  84,  II,  684,  750  (1903). 


SODIUM  PEROXIDE  169 

the  crucible  in  water,  and  titrate  in  the  cold'  with  fifth-normal  hydrochloric  acid 
solution,  using  methyl  orange  as  the  indicator. 

1  c.c.  of  fifth-normal  HC1  =  0.01340  gm.  of  Na2C2O4,  log.  12710. 

Literature:  S.  P.  L.  Sorensen,  Z.  anal.  Chem.,  36,  639  (1897);  abst.,  J.  Chem. 
Soc.,  74,  II,  185  (1898).  Z.  anal.  Chem.,  42,  333  (1903);  abst.,  J.  Chem.  Soc., 
84,  II,  684  (1903).  Z.  anal.  Chem.,  42,  512  (1903);  abst.,  J.  Chem.jSoc.,  84,  II, 
684,  750  (1903);  Z.  anal.  Chem.,  44,  156  (1905);  abst.,  J.  Chem.  Soc'.,  88, 11,415 
(1905).  G.  Lunge,  Z.  angew.  Chem.,  17,  230,  269  (1904);  abst.,  J.  Chem.  Soc., 
86,  II,  289  (1904).  Sorensen,  Z.  anal.  Chem.,  45,  217  (1906);  abst.,  J.  Chem.  Soc., 
90,  II,  389  (1906).  G.  Lunge,  Z.  angew.  Chem.,  18,  1520  (1905);  abst.,  J.  Am. 
Chem.  Soc.,  28,  1744  (1906).  Sorensen  and  Andersen,  Z.  anal.  Chem.,  44,  156 
(1905);  abst.,  J.  Chem.  Soc.,  88,  II,  415  (1905). 


SODIUM  PEROXIDE 

(Sodium  Superoxide) 
Na2O2.    Mol.  Wt.  78.0 

A  light-yellow  powder,  very  easily  soluble  in  water  with  the 
copious  evolution  of  oxygen  and  great  elevation  of  temperature. 
On  cautiously  adding  sodium  peroxide  to  a  cooled,  dilute  mineral 
acid,  hydrogen  peroxide  results.  The  preparation  contains  at  least 
92  per  cent  of  Na202. 

TESTS   OF  PURITY 

Sulphates.  —  Add  5  gm.  of  sodium  peroxide  in  small  quantities  at  a  time 
to  a  mixture  of  25  c.c.  of  hydrochloric  acid  and  100  c.c.  of  water.  The  clear 
solution  should  develop  no  precipitate  with  barium  chloride  solution  on  standing 
fifteen  hours.  (Indicating  less  than  0.014  per  cent  SO3.) 

Chlorides.  —  Add  3  gm.  of  sodium  peroxide  in  small  quantities  at  a  time  to  a 
mixture  of  20  c.c.  of  nitric  acid  and  100  c.c.  of  water.  The  clear  liquid  should 
exhibit  at  most  a  slight  opalescent  turbidity  on  the  addition  of  silver  nitrate 
solution.  (Indicating  less  than  0.0015  per  cent  Cl.) 

Phosphates.  —  Add  2.5  gm.  of  sodium  peroxide  in  small  quantities  at  a  time 
to  a  mixture  of  20  c.c.  of  nitric  acid  and  100  c.c.  of  water.  On  now  adding  25 
c.c.  of  a  solution  of  ammonium  molybdate  in  nitric  acid  and  heating  to  30°  to 
40°  C.,  no  yellow  precipitate  should  form  within  two  hours.  (Indicating  less 
than  0.006  per  cent  P2O5.) 

Nitrogen.  —  Mix  1  gm.  of  sodium  peroxide  with  0.3  gm.  of  grape  sugar,  very 
cautiously,  in  a  capacious  nickel  crucible.  Effect  the  deflagration  of  the  mixture 
by  very  gently  heating  the  bottom  of  the  covered  crucible.  When  cold,  dissolve 
the  residue  in  5  c.c.  of  water,  acidulate  with  10  c.c.  of  diluted  sulphuric  acid,  and 
overlay  10  c.c.  of  this  solution  on  5  c.c.  of  diphenylamine  solution  (see  Diphenyl- 
amine).  No  blue  color  should  develop  at  the  contact-surfaces  of  the  two  liquids. 
(Indicating  less  than  0.003  per  cent  N.) 

Silicates.  —  Add  10  gm.  of  sodium  peroxide  in  small  portions  to  a  mixture 
of  50  c.c.  of  hydrochloric  acid  and  100  c.c.  of  water,  evaporate  the  solution  to 
dryness  on  the  water-bath,  dry  the  residue  half  an  hour  at  about  120°  C.,  and 
dissolve  it  in  10  c.c.  of  hydrochloric  acid  and  90  c.c.  of  water.  Any  insoluble 
residue,  when  filtered  off,  washed  and  ignited,  should  weigh  not  more  than 
0.001  gm.  (Indicating  not  more  than  0.01  per  cent  SiOa.) 


170  CHEMICAL  REAGENTS 


Heavy  Metals.  —  On  cautiously  adding  5  gm.  of  sodium  peroxide  to  100  c.c. 
of  water,  a  perfectly  clear  and  almost  colorless  solution  should  result. 

40  c.c.  of  this  solution,  acidulated  with  10  c.c.  of  hydrochloric  acid,  should 
not  be  affected  by  hydrogen  sulphide -water.  (Indicating  none  present.) 

40  c.c.  of  the  alkaline  solution  should  develop  no  precipitate  on  the  addition 
of  a  few  drops  of  ammonium  sulphide  solution,  nor  should  the  liquid  acquire  a 
brown  or  a  green  color.  (Indicating;  none  present.) 

Quantitative  Determination.  —  The  quantitative  determination  of  sodium 
peroxide  is  most  simply  effected  by  decomposing  it  in  a  Lunge  gas  volumeter,* 
using  cobalt  nitrate  as  a  catalyzer  and  measuring  the  volume  of  oxygen  evolved' 

Introduce  0.5  gm.  of  sodium  peroxide  in  a  weighing  flask  into  the  outer 
compartment  of  the  decomposition  flask,  and  in  the  inner  place  a  mixture  of 
15  c.c.  of  diluted  sulphuric  acid  and  2  or  3  drops  of  a  saturated  solution  of  cobalt 
nitrate.  On  tilting  the  flask,  the  liquid  is  allowed  to  mix  with  the  sodium  per- 
oxide, whereby  the  decomposition  of  the  latter  is  effected. 

1  c.c,  of  0  at  0°  C,  and  760  mm.  =0.006964  gm.  of  Na202,  log.  84286. 

SODIUM  PHOSPHATE 

(Disodium  Hydrogen  Phosphate;   Secondary  Sodium  Phosphate) 
Na2HPO4+i2H2O.     Mol.  Wt.  358.24 

Colorless,  transparent  crystals,  efflorescent  in  dry  air,  and  soluble 
in  6  parts  of  water.  The  aqueous  solution  is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Carbonates  and  Sulphates.  —  20  c.c.  of  the  1  :  20  aqueous  solution  should 
not  effervesce  on  the  addition  of  1  c.c.  of  hydrochloric  acid  (indicating  less  than 
2  per  cent  CO2);  nor  should  a  precipitate  of  barium  sulphate  form  within  three 
hours  on  the  subsequent  addition  of  barium  chloride  solution.  (Indicating  less 
than  0.0075  per  cent  SO8.) 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  phosphate  in  20  c.c.  of  water, 
acidulated  with  2  c.c.  of  nitric  acid,  should  show  at  most  a  very  slight  opalescent 
turbidity  on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than  0.0015 
per  cent  Cl.) 

Nitrates.  —  To  a  solution  of  2  gm.  of  sodium  phosphate  and  a  granule  of 
sodium  chloride  in  10  c.c.  of  water  add  5  c.c.  of  diluted  sulphuric  acid,  1  drop  of 
1  :  1000  indigo  solution,  and  10  c.c.  of  concentrated  sulphuric  acid.  The  blue 
color  of  the  liquid  should  not  disappear  on  agitation.  (Indicating  less  than 
0.0016  per  cent  N2O5.) 

Heavy  Metals.  —  The  solution  of  2  gm.  of  sodium  phosphate  in  20  c.c.  of 
water,  acidulated  with  1  c.c.  of  hydrochloric  acid,  should  appear  unchanged 
on  the  addition  of  hydrogen  sulphide  water.  On  now  adding  to  the  liquid  5 
c.c.  of  ammonia  water  and  a  few  drops  of  ammonium  sulphide  solution,  no  pre- 
cipitate should  form,  nor  should  a  green  color  develop.  (Indicating  none 
present.) 

Arsenic.  —  Into  the  generating  flask  of  a  Marsh  apparatus  introduce  10  gm. 
of  arsenic-free,  metallic  zinc,  and  start  the  hydrogen  with  sulphuric  acid  (1  :  5). 


*  Lunge,  Chem.-Tech.  Untersuch,  5  ed.,  1,  158  (1905);  see  also  Olsen's  Quan- 
titative Analysis,  300  (1904). 


SODIUM  PYROPHOSPHATE  171 


Dissolve  2  gm.  of  sodium  phosphate  in  50  c.c.  of  water  and  introduce  the  solution 
in  small  portions  at  a  time  into  the  Marsh  apparatus.  No  deposit  of  arsenic 
should  be  visible  in  the  reduction  tube  within  one  hour.  (Indicating  less  than 
0.0005  per  cent  As.) 

Potassium.  —  The  color  imparted  by  sodium  phosphate  to  a  colorless  name, 
when  observed  through  cobalt  glass,  should  not  be  tinged  with  violet,  or  should 
be  only  momentarily  so.  (Indicating  less  than  0.4  percent  K.) 


SODIUM  PYROPHOSPHATE 
H2O.     Mol.  Wt.  446.24 


Colorless,  transparent  crystals,  soluble  in  10  to  12  parts  of  cold 
water,  and  in  somewhat  more  than  1  part  of  boiling  water,  but  in- 
soluble in  alcohol.  The  aqueous  solution  is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Phosphates.  —  The  1  :  20  aqueous  solution  of  sodium  pyrophosphate  should 
c;ive  a  pure  white  precipitate  with  silver  nitrate  solution.  (Indicating  less  than 
2  per  cent  P2O5  as  orthophosphate.) 

Other  Tests.  —  The  tests  as  given  under  Sodium  Phosphate  are  also  to  be  made. 


SODIUM   SULPHATE 
Na2SO4+ioH2O.    Mol.  Wt.  322.23 

Colorless,  efflorescent  crystals,  soluble  in  3  parts  of  cold,  and 
in  0.4  part  of  boiling,  water,  but  insoluble  in  alcohol.  The  aqueous 
solution  is  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Substances  Insoluble  in  Water.  —  5  gm.  of  sodium  sulphate  should  afford  a 
clear  solution  with  50  c.c.  of  water.  (Indicating  none  present.) 

Heavy  Metals.  —  The  solution  of  1  gm.  of  sodium  sulphate  in  20  c.c.  of  water 
should  not  be  affected  by  hydrogen  sulphide  water.  (Indicating  none  present.) 

The  solution  of  1  gm.  of  sodium  sulphate  in  20  c.c.  of  water  and  boiled  with 
a  few  drops  of  nitric  acid  should  not  be  reddened  on  the  addition  of  potassium 
sulphocyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Chlorides.  —  The  solution  of  1  gm.  of  sodium  sulphate  in  20  c.c.  of  water 
should  not  be  affected  by  silver  nitrate  solution.  (Indicating  less  than  0.001 
per  cent  Cl.) 

Calcium  and  Magnesium.  —  The  1  :  20  aqueous  solution  should  not  be 
affected  by  ammonium  oxalate  solution  (indicating  less  than  0.02  per  cent  Ca); 
nor,  after  adding  ammonia  water,  by  ammonium  phosphate  solution.  (Indicating 
less  than  0.005  per  cent  Mg.) 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  metallic  zinc  into  the  generating 
flask  of  a  Marsh  apparatus,  and  start  the  hydrogen  with  diluted  sulphuric  acid 
(1  :  5).  Dissolve  2  gm.  of  sodium  sulphate  in  20  c.c.  of  water  and  introduce  the 


172  CHEMICAL  REAGENTS 


solution  in  small  portions  at  a  time  into  the  Marsh  apparatus.  No  deposit 
of  arsenic  should  be  visible  in  the  reduction  tube  within  one  hour.  (Indicating 
less  than  0.0005  per  cent  As.) 


SODIUM   SULPHIDE 
Na2S+9H2O.     Mol.  Wt.  240.2 

Colorless,  transparent  crystals,  easily  and  clearly  soluble  in  water. 
The  aqueous  solution  is  alkaline  to  litmus  paper.  The  preparation 
contains  at  least  97  per  cent  of  Na2S+9H2O. 

TESTS   OF  PURITY 

Nitrogen.  —  To  the  solution  of  10  gm.  of  sodium  sulphide  in  100  c.c.  of  water 
in  a  distillation  flask  add  2  gm.  of  Devarda's  metal  and  50  c.c.  of  nitrogen-free 
sodium  hydroxide  solution  (sp.gr.  1.3),  and  connect  the  flask  with  a  bulb  tube, 
a  condenser,  and  a  receiver  containing  2  to  3  c.c.  of  fifth-normal  hydrochloric 
acid  solution,  and  10  c.c.  of  water.  After  allowing  the  mixture  to  stand  one  to 
two  hours,  distil  off  about  50  c.c.  and  titrate  the  distillate  with  fifth-normal 
potassium  hydroxide  solution,  using  methyl  orange  as  indicator.  The  amount 
of  fifth-normal  hydrochloric  acid  solution  found  to  have  been  neutralized  by  the 
ammonia  should  be  at  most  0.2  c.c.  (Indicating  not  more  than  0.0056  per  cent  N.) 

Quantitative  Determination;  Sulphites,  and  Th'iosulphates.  —  (a)  Dissolve 
1  gm.  of  sodium  sulphide  in  water  and  dilute  to  100  c.c.  Allow  20  c.c.  of  this 
solution  to  run  into  a  mixture  of  20  c.c.  of  decinormal  iodine  solution,  and 
100  c.c.  of  water.  After  adding  3  c.c.  of  hydrochloric  acid,  titrate  the  excess  of 
iodine  with  decinormal  sodium  thiosulphate  solution,  using  starch  solution  as 
the  indicator. 

1  c.c.  of  decinormal  1=0.0120105  gm.  of  Na2S+9H2O,  log.  07956. 

(6)  To  a  solution  of  1  gm.  of  sodium  sulphide  in  100  c.c.  of  water,  add  2  gm. 
of  crystallized  zinc  sulphate  dissolved  in  150  c.c.  of  water;  shake  vigorously, 
allow  to  stand  half  an  hour,  and  then  filter.  Titrate  50  c.c.  of  the  filtrate  with 
decinormal  iodine  solution,  using  starch  solution  as  the  indicator.  Not  more 
than  0.1  c.c.  of  decinormal  iodine  solution  should  be  required.  (Indicating  not 
more  than  0.08  per  cent  S  as  sulphites  and  thiosulphates.) 


SODIUM   SULPHIDE   SOLUTION 

Sodium  sulphide  solution  contains  5  per  cent  of  Na2§  and  is 
used  for  determination  of  nitrogen  according  to  Kjeldahl. 

TEST   OF  PURITY 

Nitrogen.  —  The  test  for  nitrogen  is  to  be  carried  out  as  described  under 
Potassium  Sulphide  Solution. 


SODIUM  SULPHITE  173 


SODIUM     SULPHITE 
I 

SODIUM   SULPHITE,   CRYSTALS 
Na2SO3+7H2O.     Mol.  Wt.  252.18 

Colorless,  prismatic  crystals,  efflorescent  in  air,  and  easily  soluble 
in  water.  The  aqueous  solution  is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Chlorides.  —  Dissolve  1  gm.  of  sodium  sulphite  in  10  c.c.  of  water,  add  10 
c.c.  of  perhydrol  (hydrogen  peroxide,  30  per  cent)  and  a  solution  of  potassium 
hydroxide,  purest,  to  alkaline  reaction,  and  evaporate  the  solution  on  the  water- 
bath.  Dissolve  the  residue  in  20  c.c.  of  water,  acidulate  with  nitric  acid,  and  add 
silver  nitrate  solution.  At  most  a  slight  opalescence  should  develop.  (Indicating 
less  than  0.002  per  cent  Cl.) 

Heavy  Metals.  —  Dissolve  2  gm.  of  sodium  sulphite  in  10  c.c.  of  water,  add 
20  c.c.  of  hydrochloric  acid,  evaporate  on  the  water-bath,  and  dissolve  the  residue 
in  20  c.c.  of  water.  On  adding  hydrogen  sulphide  water  to  this  solution  no  change 
should  occur;  and  after  adding  ammonia  water  and  ammonium  sulphide  solution, 
no  precipitate  should  form.  (Indicating  none  present.) 

Arsenic.  —  Introduce  5  grn.  of  sodium  sulphite  in  small  portions  into  25  c.c. 
of  nitric  acid  (sp.gr.  1.3).  Thereupon  add  5  c.c.  of  concentrated  sulphuric  acid, 
and  evaporate  the  mixture  on  the  water-bath  as  far  as  possible,  and  then  on  the 
sand-bath  until  sulphuric  acid  vapors  begin  to  be  evolved.  Dissolve  the  residue 
in  50  c.c.  of  water. 

Start  the  evolution  of  hydrogen  in  a  Marsh  apparatus  by  means  of  20  gm. 
of  granulated,  arsenic-free  zinc  and  diluted  sulphuric  acid  (1  :  5),  and  introduce 
in  small  portions  into  the  generating  flask  of  the  apparatus  the  solution  to  be 
tested.  No  deposit  of  arsenic  should  be  visible  in  the  reduction  tube  within  one 
hour.  (Indicating  less  than  0.0002  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  sulphite  in  boiled 
water  and  dilute  to  100  c.c.  Allow  the  solution  to  run  from  a  burette  into  a 
mixture  of  30  c.c.  of  decinormal  iodine  and  5  c.c.  of  hydrochloric  acid,  with  con- 
stant agitation,  until  complete  decolorization  occurs. 

1  c.c.  of  decinormal  1=0.012609  gm.  of  Na2S03+7H20,  log.  10068. 

II 
SODIUM   SULPHITE,  DRIED 

A  white  powder,  containing  85  to  90  per  cent  of  Na2SOs. 

TESTS  OF  PURITY 

The  tests  for  chlorides,  heavy  metals,  and  arsenic,  as  given  under  Sodium 
Sulphite,  Crystals,  are  to  be  made;  but  for  1  gm.  of  the  crystals  use  0.5  gm.  of 
the  sodium  sulphite,  dried. 


174  CHEMICAL  REAGENTS 

The  quantitative  determination  is  to  be  made  as  described  under  Sodium 
Sulphite,  Crystals. 

1  c.c.  of  decinormal  1=0.0063035  gm.  of  Na^SOs,  log.  79958. 


SODIUM  THIOSULPHATE 

(Sodium  Hyposulphite) 
Na2S2O3+5H2O.    Mol.  Wt.  248.22 

Colorless  and  odorless  crystals,  permanent  in  the  air  at  ordinary 
temperatures.  Sodium  thiosulphate  liquefies  at  50°  C.  in  its  own 
water  of  crystallization,  and  is  soluble  in  less  than  1  part  of  cold 
water.  The  1  :  1  aqueous  solution  is  slightly  alkaline  to  litmus 
paper.  For  making  the  tests  the  solutions  are  to  be  made  with 
freshly  boiled  water. 

TESTS   OF  PURITY 

Carbonates,  Sulphates,  and  Sulphites.*  —  To  a  solution  of  3  gm.  of  sodium 
thiosulphate  in  50  c.c.  of  water,  add  decinormal  iodine  solution  (about  120  c.c.) 
until  the  liquid  has  a  slight  yellow  color;  on  now  adding  barium  chloride  solution, 
no  turbidity  should  ensue.  (Indicating  less  than  0.17  per  cent  CO2,  and  less 
than  0.01  per  cent  sulphates  and  sulphites  as  SO3.) 

Free  Alkali.  —  The  solution  of  1  gm.  of  sodium  thiosulphate  in  10  c.c.  of  water 
should  not  be  reddened  by  phenolphthalein  solution.  (Indicating  less  than  0.01 
per  cent  as  NaOH.) 

Sulphides.  —  The  solution  of  1  gm.  of  sodium  thiosulphate  in  10  c.c.  of  water 
should  not  change  in  appearance  on  the  addition  of  zinc  sulphate  solution. 
(Indicating  less  than  0.013  per  cent  S.) 

Calcium.  —  The  solution  of  1  gm.  of  sodium  thiosulphate  in  20  c.c.  of  water 
should  not  be  rendered  turbid  on  the  addition  of  ammonia  water  and  ammonium 
oxalate  solution.  (Indicating  less  than  0.02  per  cent  Ca.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  thiosulphate  in  100 
c.c.  of  water,  and  titrate  with  decinormal  iodine  solution,  using  starch  solution  as 
the  indicator. 

1  c.c.  of  decinormal  1  =  0.024822  gm.  of  Na2S2O3+5H20,  log.  39484. 


*  Concerning  a  new  titrimetric  determination  of  thiosulphate  in  the  presence 
of  sulphite,  see  A.  Gutman,  Z.  anal.  Chem.,  46,  485  (1907);  abst.,  J.  Chem.  Soc., 
92,  II,  812  (1907). 

Regarding  the  determination  of  sulphite  in  the  presence  of  thiosulphate,  see 
G.  Htibener,  Chem.  Ztg.,  30,  58  (1906);  abst.,  J.  Chem.  Soc.,  90,  II,  196  (1906). 


SODIUM  TUNGSTATE  175 

SODIUM  TUNGSTATE 

(Sodium  Wolframate) 
Na2WO4+ 2H2O.*    Mol.  Wt.  330.03 

Colorless  prisms  or  rhombic  plates,  soluble  in  4  parts  of  water. 
The  aqueous  solution  is  alkaline  to  litmus  paper. 

TESTS   OF  PURITY 

Water.  —  After  gently  igniting  1  gm.  of  sodium  tungstate,  the  residue  should 
weigh  0.88  gm.  (Indicating  12  per  cent  water.) 

Chlorides.  —  Dissolve  1  gm.  of  sodium  tungstate  in  20  c.c.  of  water,  add  5 
c.c.  of  nitric  acid,  and  filter.  The  filtrate  should  acquire  at  most  a  slight  opalescent 
turbidity  within  ten  minutes  alter  adding  a  few  drops  of  silver  nitrate  solution. 
(Indicating  less  than  0.001  per  cent  Cl.) 

Sulphates.  —  Dissolve  1  gm.  of  sodium  tungstate  in  25  c.c.  of  water,  add  5  c.c. 
of  nitric  acid,  boil  for  ten  to  fifteen  minutes,  and  then  filter.  20  c.c.  of  the 
filtrate  should  not  immediately  be  rendered  turbid  on  the  addition  of  barium 
nitrate  solution.  (Indicating  less  than  0.075  per  cent  SO3.) 

Quantitative  Determination.  —  Dissolve  1  gm.  of  sodium  tungstate  in  10  c.c. 
of  water,  add  10  c.c.  of  hydrochloric  acid,  evaporate  on  the  water-bath  to  dryness, 
and  heat  the  residue  for  half  an  hour  at  120°  C.  Treat  the  residue  with  20  c.c. 
of  hydrochloric  acid,  and  repeat  the  entire  operation  three  or  four  times.  Finally 
digest  the  residue  with  ammonium  nitrate  solution  to  which  a  little  nitric  acid 
has  been  added,  filter,  wash  the  tungstic  acid  with  dilute  nitric  acid,  dry,  ignite, 
and  weigh  the  residue.  The  latter  should  weigh  at  least  0.69  gm. 


SODIUM  AND  AMMONIUM  PHOSPHATE 

(Microcosmic  Salt) 
NH4NaHPO4+4H2O.    Mol.  Wt.  209.15 

Colorless,  monoclinic  crystals,  soluble  in  5  parts  of  water.  The 
aqueous  solution  is  alkaline  to  litmus  paper.  Sodium  and  ammonium 
phosphate  when  fused  on  a  platinum  wire  should  yield  a  clear  and 

colorless  bead. 

TESTS   OF  PURITY 

The  tests  given  under  Sodium  Phosphate  are  to  be  made,  observing  the 
conditions  there  described. 


*  The    preparation    contains    small    amounts    of    sodium    paratungstate 

(NaioWi2O4i+28H2O). 


176  CHEMICAL  REAGENTS 


SODIUM  AND  POTASSIUM  CARBONATE,  FUSED, 
ANHYDROUS 

White  sticks  used    for  making  carbon  dioxide   free  from  air, 
according  to  Kreussler. 


SODIUM-COBALTIC  NITRITE  SOLUTION 

A  solution  of  10  gm.  of  cobalt  acetate  in  25  c.c.  of  water  is  mixed 
with  a  solution  of  20  gm.  of  sodium  nitrite  in  40  c.c.  of  water,  and 
then  acidulated  with  5  c.c.  of  dilute  acetic  acid. 


TETRAMETHYLPARAPHENYLENEDIAMINE  HYDRO- 
CHLORIDE 

(Paratetramethylphenylenediamine  Hydrochloride) 

(CH3)2NCeH4N(CH3)22HCl.     Mol.  Wt.  237.08 

A  white  or  slightly  colored,  crystalline  powder,  easily  soluble  in 
water,  more  difficultly  in  alcohol.  It  should  be  protected  from  light 
and  moisture. 

TESTS   OF  PURITY 

Inorganic  Matter.  —  On  igniting  1  gm.  of  tetramethylparaphenylenediamine 
hydrochloride,  no  weighable  residue  should  remain.  (Indicating  less  than 
0.05  per  cent.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  tetramethylparaphenylene- 
diamine  hydrochloride  in  50  c.c.  of  alcohol  (85  per  cent  by  weight)  in  a  glass- 
stoppered  flask,  and  titrate  the  solution  with  fifth-normal  potassium  hydroxide 
solution,  using  Poirrier's  blue  as  the  indicator. 

1  c.c.  of  fifth-normal  KOH  =  0.023708  gm.  of  (CHi)jNCeH4N(CH,)j2HCi; 
log.  37489. 

NOTE.  —  Regarding  the  use  of  tetramethylparaphenylenediamine  hydro- 
chloride  as  a  reagent,  see  Wurster.,  Ber.,  19,  3195  (1886);  abst.,  J.  Chem.  Soc., 
52,  295  (1887);  Ber.,  21,  921  (1888);  dbst.,  J.  Chem.  Soc.,  54,  627  (1888). 


THYMOL 

C6H3(CH3)(OH)(C3H7)i  13:4.     Mol.  Wt.  150.11 

Colorless,  hexagonal  crystals,  easily  soluble  in  alcohol,  ether,  and 
chloroform,  but  very  difficultly  soluble  in  water  (1  :  1100).  Thymol 
melts  at  50°  to  51°  C.,  and  boils  at  228°  to  230°  C. 


TIN  •      177 


TESTS   OF  PURITY 

Inorganic  Matter.  —  1  gm.  of  thymol  on  heating  should  volatilize  without 
leaving  a  weighable  residue.  (Indicating  less  than  0.05  per  cent.) 

Free  Acids.  —  Blue  litmus  paper  should  not  be  reddened  by  the  aqueous 
or  alcoholic  solution.  (Indicating  none  present.) 

Phenol.  —  The  cold,  saturated,  aqueous  solution  acquires  a  milky  turbidity 
on  the  addition  of  bromine  water,  but  should  show  no  crystalline  precipitate. 
Nor  should  the  aqueous  solution  of  thymol  afford  a  violet  color  with  ferric 
chloride  solution.  (Indicating  none  present.) 


TIN 

Sn.    Atomic  Wt.  119 

A  soft,  almost  silver-white  metal,  melting  at  231°  C.  Tin  dis- 
solves in  hot  hydrochloric  acid  with  the  formation  of  stannous 
chloride.  Hot  concentrated  nitric  acid  converts  it  into  insoluble 

meta-stannic  acid.  » 

TESTS   OF  PURITY 

Lead,  Copper,  Iron,  and  Zinc.  —  Digest  5  gm.  of  the  tin  with  40  c.c.  of  nitric 
acid  (sp.gr.  1.4)  on  the  water-bath  until  the  conversion  of  the  metal  into  a  white 
powder  is  complete.  Then  evaporate  completely,  stir  the  residue  with  10  c.c.  of 
nitric  acid  (sp.gr.  1.150  to  1.152)  and  50  c.c.  of  water,  and  filter.  To  the  filtrate 
add  1  c.c.  of  diluted  sulphuric  acid,  evaporate  on  the  water-bath  as  far  as  pos- 
sible, and  then  take  up  the  residue  with  10  c.c.  of  water.  In  case  the  solution 
is  not  perfectly  clear,  filter.  The  weight  of  the  insoluble  matter  after  ignition 
should  not  exceed  0.0005  gm.  (PbSO4).  (Indicating  not  more  than  0.00683  per 
cent  Pb.)  To  the  filtrate  add  ammonia  water  to  alkaline  reaction.  The  liquid 
should  not  acquire  a  blue  color.  (Indicating  less  than  0.0004  per  cent  Cu.) 
Now  add  ammonium  sulphide  solution,  and  allow  the  mixture  to  stand  for  four  to 
five  hours  at  about  50°  C.  Should  any  precipitate  form,  its  weight  after  ignition 
should  not  exceed  0.002  gm.  (Indicating  not  over  0.04  per  cent  Fe  and  Zn  as 
sulphides.) 

Antimony.  —  Heat  on  the  water-bath  5  gm.  of  tin  and  50  c.c.  of  hydrochloric 
acid,  adding  potassium  chlorate  in  small  portions  until  solution  results.  Now 
heat  the  solution  nearly  to  boiling  and  add  bright  piano-wire  until  the  latter 
ceases  to  dissolve.  (The  piano-wire  used  in  this  test  should  be  soluble  without 
residue  in  dilute  hydrochloric  acid.)  From  this  treatment  no  precipitate  should 
result,  or  only  a  very  slight  black  precipitate.  (Indicating  at  most  a  trace.) 

Arsenic.  —  Digest  5  gm.  of  tin  on  the  water-bath  with  40  c.c.  of  nitric  acid 
(sp.gr.  1.4)  until  the  metal  is  completely  changed  to  a  white  powder.  Evaporate 
completely,  treat  the  residue  with  10  c.c.  of  nitric  acid  (sp.gr.  1.150  to  1.152) 
and  50  c.c.  of  water,  and  filter.  Mix  the  filtrate  with  5  c.c.  of  concentrated  sul- 
phuric acid  and  evaporate,  at  first  on  a  water-bath,  then  on  a  sand-bath,  until 
fumes  of  sulphuric  acid  begin  to  be  evolved.  After  cooling,  dissolve  the  residue 
in  50  c.c.  of  water. 

Start  the  evolution  of  hydrogen  in  a  Marsh  apparatus  by  means  of  20  gm. 
of  granulated  arsenic-free  zinc  and  diluted  sulphuric  acid  (1  :  5),  and  gradually 
add  the  solution  of  the  residue  to  the  generating  flask  of  the  apparatus.  After 
one  hour  there  should  be  visible  in  the  reduction  tube  at  most  a  slight  deposit 
of  arsenic.  (Indicating  at  most  a  trace.) 


178  CHEMICAL  REAGENTS 

TIN  CHLORIDE 

(Stannous  Chloride) 
SnCl2+2H2O.    Mol.  Wt.  225.95 

Colorless  crystals,  easily  and  completely  soluble  in  alcohol,  and 
in  water  acidulated  with  hydrochloric  acid.  Stannous  chloride  solu- 
tion is  decomposed  by  much  water,  with  the  separation  of  a  basic 
stannous  chloride. 

TESTS  OF  PURITY 

Sulphates.  —  Dissolve  1  gm.  of  stannous  chloride  in  5  c.c.  of  hydrochloric 
acid  (sp.gr.  1.19),  and  dilute  with  50  c.c.  of  water.  The  solution  should  not  be 
affected  by  barium  chloride  solution.  (Indicating  less  than  0.125  per  cent  SO3.) 

Ammonium  Compounds.  —  On  heating  1  gm.  of  stannous  chloride  with  10 
c.c.  of  sodium  hydroxide  solution  (sp.gr.  1.3),  no  vapors  of  ammonia  should  be 
evolved  (to  be  ascertained  by  moist  litmus  paper).  (Indicating  less  than  0.0035 
per  cent  NH3.) 

Earths,  Alkalies,  and  Iron.  —  Dissolve  2  gm.  of  stannous  chloride  in  10  c.c. 
of  hydrochloric  acid  (sp.gr.  1.19),  dilute  the  solution  with  100  c.c.  of  water, 
and  pass  into  the  solution  hydrogen  sulphide  gas  until  all  the  tin  has  been  pre- 
cipitated. Filter  off  the  precipitate,  evaporate  the  filtrate,  and  ignite  the  residue; 
the  weight  of  the  ignited  residue  should  not  exceed  0.002  gm.  (Indicating  not 
more  than  0.1  per  cent  earths  and  alkalies.)  On  heating  the  ignited  residue  with 
1  c.c.  of  hydrochloric  acid,  then  diluting  with  20  c.c.  of  water,  and  adding 
potassium  sulpho-cyanate  solution,  at  most  a  slight  red  color  should  develop. 
(Indicating  less  than  0.00075  per  cent  Fe.) 

Arsenic.  —  Boil  2  gm.  of  stannous  chloride  with  10  c.c.  of  hydrochloric  acid 
(sp.gr.  1.19)  for  several  minutes.  The  liquid  should  remain  clear  and  colorless 
for  one  hour.  (Indicating  less  than  0.00075  per  cent  As.) 

Quantitative  Determination.  —  Dissolve  0.5  gm.  of  stannous  chloride  in  2 
c.c.  ol  hydrochloric  acid  (sp.gr.  1.19)  and  dilute  the  solution  with  50  c.c.  of  water. 
Then  add  5  gm.  of  potassium  and  sodium  tartrate,  and  sodium  bicarbonate  until 
the  solution  is  alkaline  to  litmus  paper.  Now  titrate  with  decinormal  solution  of 
iodine,  using  starch  solution  as  the  indicator. 

1  c.c.  of  decinormal  1  =  0.0112976  gm.  of  SnCl2+2H2O,  log.  05299. 


TIN   CHLORIDE   SOLUTION 
(Stannous  Chloride  Solution) 

A  slightly  yellow,  refractive  liquid,  the  specific  gravity  of  which 
should  not  be  less  than  1.90.  It  is  obtained  by  stirring  5  parts  of 
stannous  chloride  with  1  part  of  hydrochloric  acid,  and  then  saturat- 
ing the  mixture  with  dry  hydrochloric  acid  gas. 


URANIUM  ACETATE  179 


TESTS   OF  PURITY 

Substances  Precipitated  by  Alcohol.  —  On  mixing  stannous  chloride  solution 
with  10  times  its  volume  of  85  per  cent  (by  weight)  alcohol,  no  turbidity  should 
ensue  on  standing  for  one  hour.  (Indicating  none  present.) 

Sulphuric  Acid.  —  5  c.c.  of  stannous  chloride  solution  diluted  with  50  c.c.  of 
water  should  not  become  turbid  within  ten  minutes  after  the  addition  of  barium 
nitrate  solution.  (Indicating  less  than  0.002  per  cent  SO3.) 


URANIUM  ACETATE,  FREE  FROM  SODIUM 

(Uranyl  Acetate) 
UO2(C2H3O2)2-f  2H2O.    Mol.  Wt.  424.58 

A  yellow,  crystalline  powder,  easily  soluble  in  water.  As  the 
preparation  nearly  always  contains  some  basic  salt,  a  clear  solution 
is  obtained  only  on  adding  a  little  acetic  acid. 

TESTS   OF  PURITY 

Sulphates.  —  The  solution  of  1  gm.  of  uranium  acetate  in  20  c.c.  of  water 
and  2  to  3  c.c.  of  diluted  acetic  acid  should  not  be  affected  by  barium  chloride 
solution.  (Indicating  less  than  0.0035  per  cent  SO3.) 

Sodium.  —  Dissolve  5  gm.  of  uranium  acetate  in  200  c.c.  of  water,  with  the 
aid  of  10  c.c.  of  diluted  acetic  acid.  Add  to  the  boiling  solution  an  excess  of 
ammonia  water,  filter,  and  evaporate  the  filtrate  to  dryness.  Ignite  the  residue, 
dissolve  it  in  water,  and  then  titrate  with  normal  hydrochloric  acid  solution, 
using  methyl  orange  as  the  indicator.  Not  more  than  0.1  c.c.  of  normal  hydro- 
chloric acid  solution  should  be  required  to  produce  the  red  color.  (Indicating 
not  more  than  0.046  per  cent  Na.) 

Earths.  —  The  solution  of  1  gm.  of  uranium  acetate  in  20  c.c.  of  water  and 
2  to  3  c.c.  of  diluted  acetic  acid  should  not  appear  changed  within  one  minute 
on  adding  ammonia  water  and  ammonium  carbonate  solution  in  excess.  (Indi- 
cating less  than  0.005  per  cent  earths  as  Ca.) 

Uranous  Salt.  —  The  solution  of  1  gm.  of  uranium  acetate  in  20  c.c.  of  water 
and  1  c.c.  of  diluted  sulphuric  acid  should  be  colored  red  on  the  addition  of  0.1 
to  0.2  c.c.  of  decinormal  potassium  permanganate  solution.  (Indicating  not 
over  0.2385  per  cent  UIV.) 

Foreign  Metals.  —  (a)  On  heating  to  boiling  a  solution  of  5  gm.  of  uranium 
acetate  in  100  c.c.  of  water  and  5  c.c.  of  hydrochloric  acid,  no  change  should 
appear  within  one  minute  on  passing  into  the  solution  hydrogen  sulphide  gas. 
(Indicating  none  present.) 

(6)  On  adding  to  the  liquid  obtained  under  the  test  for  earths,  2  or  3  drops 
of  ammonium  sulphide  solution,  no  dark-brown  color  should  develop,  nor  should 
a  precipitate  form.  (Indicating  none  present,) 


1 80  CHEMICAL  REAGENTS 

URANIUM  NITRATE 

(Uranyl  Nitrate) 
UO2(NO3)2+6H2O.    Mol.  Wt.  502.62 

Yellow  crystals,  having  a  greenish  luster  by  reflected  light,  and 
efflorescing  superficially  in  dry  air.  Uranium  nitrate  is  easily 
soluble  in  water,  alcohol,  and  ether.  The  aqueous  solution  is  acid 

to  litmus  paper. 

TESTS   OF  PURITY 

Sulphates.  —  The  1  :  20  aqueous  solution  should  not  develop  a  turbidity 
within  fifteen  minutes  on  adding  barium  chloride  solution.  (Indicating  less  than 
0.0025  per  cent  SO3.) 

Alkali  Salts.  —  Ignite  1  gm.  of  uranium  nitrate,  pulverize  the  residue,  ignite 
again,  and  treat  the  residue  with  20  c.c.  of  water.  On  filtering,  and  evaporating 
the  filtrate,  no  weighable  residue  should  remain.  (Indicating  less  than  0.05  per 
cent.)  .  ^  . 

Earths.  —  The  solution  of  1  gm.  of  uranium  nitrate  in  20  c.c.  of  water  should 
not  appear  changed  within  one  minute  on  the  addition  of  ammonia  water  and 
ammonium  carbonate  solution  in  excess.  (Indicating  less  than  0.005  per  cent 
earths  as  Ca.) 

Uranous  Salt.  —  The  solution  of  1  gm.  of  uranium  nitrate  in  20  c.c.  of  water 
and  1  c.c.  of  diluted  sulphuric  acid  should  be  colored  red  on  the  addition  of  0.1 
to  0.2  c.c.  of  decinormal  potassium  permanganate  solution.  (Indicating  not  more 
than  0.2385  per  cent  UIV.) 

Foreign  Metals.  —  (a)  The  liquid  obtained  under  the  test  for  earths,  when 
treated  with  2  or  3  drops  of  ammonium  sulphide  solution,  should  not  acquire  a 
dark-brown  color,  nor  should  it  develop  a  precipitate.  (Indicating  none  present.) 

(6)  On  heating  to  boiling  a  solution  of  5  gm.  of  uranium  nitrate  in  100  c.c. 
of  water  and  5  c.c.  of  hydrochloric  acid,  and  passing  hydrogen  sulphide  gas  into 
the  solution,  no  change  should  appear.  (Indicating  none  present.) 

WATER,  DISTILLED 

H2O.     Mol.  Wt.  18.02 
Distilled  water  must  be  neutral  to  litmus  paper. 

TESTS   OF  PURITY 

Ammonia  and  Ammonium  Compounds.  —  50  c.c.  of  the  water  should  show 
no  change  on  the  addition  of  10  to  15  drops  of  Nessler's  reagent.  (Indicating 
less  than  0.00002  per  cent  NH8.) 

Chlorides.  —  100  c.c.  of  water  should  show  no  change  on  adding  a  few  drops 
of  nitric  acid  followed  by  silver  nitrate  solution.  (Indicating  less  than  0.00001 
per  cent  Cl.) 

Sulphates.  —  On  adding  1  c.c.  of  hydrochloric  acid  and  some  barium  chloride 
solution  to  100  c.c.  of  water,  no  precipitate  of  barium  sulphate  should  form  on 
standing  fifteen  hours.  (Indicating  less  than  0.0002  per  cent  SO3.) 


XY LI  DINE  181 


Nitrates.  —  Introduce  5  c.c.  of  diphenylamine  solution  (see  Diphenylamine) 
into  a  test-tube,  and  overlay  it  with  10  c.c.  of  water.  No  blue  color  should  form 
at  the  contact-surfaces  of  the  two  liquids.  (Indicating  less  than  0.0007  per  cent 
N205.) 

Non-volatile  Matter.  —  100  c.c.  of  the  water  evaporated  on  the  water-bath 
should  leave  no  weighable  residue.  (Indicating  less  than  0.0005  per  cent.) 

Heavy  Metals  and  Calcium.  —  100  c.c.  of  the  water  should  show  no  change 
with  hydrogen  sulphide  water  (indicating  no  heavy  metals  present),  or  ammonia 
water  with  ammonium  sulphide,  or  ammonium  oxalate  solution.  (Indicating 
less  than  0.0002  per  cent  Ca.) 

Substances  Oxidizable  by  Permanganate  (Organic  Matter,  Nitrites,  etc.).  — 
Heat  to  boiling  100  c.c.  of  the  water  with  1  c.c.  of  16  per  cent  of  sulphuric  acid, 
add  1  drop  of  potassium  permanganate  solution  (1  :  1000),  and  maintain  the 
boiling  for  three  minutes.  The  liquid  should  not  be  decolorized.  (Indicating 
none  present.) 

XYLIDINE 

C6H3(CH3)2(NH2).     Mol.  Wt.  121.10 

A  yellow  to  yellowish-brown  liquid,  having  a  specific  gravity  of 
0.981  to  0.984,  and  boiling  at  212°  to  215°  C. 

TEST   OF  PURITY 

Substances  Insoluble  in  Hydrochloric  Acid.  —  10  c.c.  of  xylidine  should  afford 
a  perfectly  clear  solution  with  a  mixture  of  10  c.c.  of  hydrochloric  acid  and  10 
c.c.  of  water.  (Indicating  none  present.) 


ZINC 

Zn.    Atomic  Wt.  65.37 
A  shining,  bluish-white  metal. 


ZINC,    FREE    FROM    ARSENIC,    SULPHUR,    PHOSPHORUS, 

AND  IRON 

This  grade  of  zinc  occurs  in  three  forms,  granulated,  thin  sticks, 

and  thick  sticks. 

TESTS   OF  PURITY 

Arsenic.  —  Introduce  20  gm.  of  zinc  into  the  generating  flask  of  a  Marsh 
apparatus,  and  start  the  hydrogen  with  arsenic-free,  dilute  sulphuric  acid  (1  :  5), 
maintaining  the  flow  of  gas  until  the  metal  is  almost  completely  dissolved.  At 
the  end  of  the  test,  no  deposit  of  arsenic  should  be  visible  within  the  reduction 
tube.  (Indicating  less  than  0.000025  per  cent  As.) 


182  CHEMICAL  REAGENTS 


Matter  Oxidizable  by  Potassium  Permanganate.  —  Dissolve  10  gm.  of  zinc 
in  a  mixture  of  60  c.c.  of  water  and  15  c.c.  of  pure  sulphuric  acid  (sp.gr.  1.84) 
in  a  flask  provided  with  a  rubber  valve;  no  black  flocks  should  remain  undissolved. 
As  soon  as  the  zinc  has  dissolved,  add  to  the  solution,  drop  by  drop,  decinormal 
potassium  permanganate  solution.  Not  more  than  0.1  c.c.  should  be  required  to 
produce  a  distinct  pink  color.  Should  more  of  the  permanganate  solution  be 
required,  the  dilute  sulphuric  acid  (15  c.c.  of  sulphuric  acid  and  60  c.c.  of  water) 
should  be  titrated  for  the  purpose  of  control,  without  zinc,  using  the  same  solution 
of  decinormal  potassium  permanganate.  (Indicating  less  than  0.0056  per  cent 
oxidizable  matter  as  Fe.) 

Compounds  of  Sulphur,  Phosphorus,  etc.  —  Into  a  narrow  test-tube  introduce 
1  gm.  of  zinc  together  with  5  to  10  c.c.  of  dilute,  arsenic-free  sulphuric  acid,  and 
in  the  upper  part  of  the  tube  insert  a  plug  of  cotton,  which  serves  to  hold  back 
the  water  carried  off  by  the  escaping  hydrogen.  Over  the  mouth  of  the  tube 
lay  a  small  piece  of  filter  paper  which  has  been  moistened  with  1  :  1  silver  nitrate 
solution,  and  carefully  dried.  The  reaction  is  allowed  to  proceed  in  a  dark  place 
which  is  perfectly  free  from  hydrogen  sulphide.  On  standing  two  hours,  the 
silver  nitrate  paper  should  show  neither  a  yellow  nor  a  black  color.  (Indicating 
none  present,) 

II 
ZINC,  FREE  FROM  ARSENIC,  NEARLY  FREE  FROM  IRON 

This  grade  of  zinc  is  in  various  forms,  granulated,  thick  sticks, 
thin  sticks,  plates,  powder,  and  turnings. 

TESTS  OF  PURITY 

Arsenic.  —  The  test  is  carried  out  as  described  under  Zinc,  Free  from  Arsenic, 
Sulphur,  Phosphorus,  and  Iron. 

Matter  Oxidizable  by  Permanganate.  —  Dissolve  10  gm.  of  zinc  in  a  mixture 
of  60  c.c.  of  water  and  15  c.c.  of  pure  concentrated  sulphuric  acid  in  a  flask 
provided  with  a  rubber  valve.  The  solution  should  contain  only  a  very  slight 
quantity  of  undissolved  black  flocks.  As  soon  as  the  zinc  has  dissolved,  add 
to  the  solution,  drop  by  drop,  decinormal  potassium  permanganate  solution. 
Not  more  than  0.5  c.c.  should  be  required  to  produce  a  distinct  pink  color. 
(Indicating  less  than  0.028  per  cent  oxidizable  matter  as  Fe.) 

This  grade  of  zinc  in  powder  form  should,  in  addition  to  the  above,  be  tested 
as  follows: 

Chlorides.  —  Dissolve  5  gm.  of  the  zinc  in  a  mixture  of  50  c.c.  of  nitric  acid 
and  100  c.c.  of  water.  This  solution  should  not  show  more  than  a  slight  opalescent 
turbidity  on  the  addition  of  silver  nitrate  solution.  (Indicating  less  than  0.0005 
per  cent  Cl.) 

Ill 
ZINC,  FREE  FROM  ARSENIC 

This  zinc  is  used  in  the  following  forms:  granulated,  thick  sticks, 
thin  sticks,  powder  and  turnings. 


ZINC  DUST  183 


TEST   OF  PURITY 

Arsenic.  —  This  test  is  carried  out  as  described    under    Zinc,  Free  from 
Arsenic,  Sulphur,  Phosphorus,  and  Iron. 


IV 
ZINC  DUST 

A  fine,  gray  powder,  containing  about  90  per  cent  of  metallic 

zinc. 

TESTS   OF  PURITY 

Nitrogen.  —  Dissolve  20  gm.  of  zinc  dust  in  a  mixture  of  20  c.c.  of  sulphuric 
acid  (sp.gr.  1.84)  and  200  c.c.  of  water  with  the  aid  of  heat.  In  case  the  zinc 
dust  dissolves  with  great  difficulty  add  a  few  drops  of  platinum  chloride  solution, 
free  from  nitric  acid.  After  cooling,  add  to  the  solution  100  c.c.  of  sodium 
hydroxide  solution  I,  distil  off  about  75  c.c.  and  collect  the  distillate  in  a  receiver 
containing  10  c.c.  of  water  and  2  to  3  c.c.  of  fifth-normal  hydrochloric  acid 
solution.  Titrate  the  distillate  with  fifth-normal  potassium  hydroxide  solution, 
using  methyl  orange  as  the  indicator.  Not  more  than  0.3  c.c.  of  the  acid  should 
have  been  neutralized  by  the  ammonia.  (Indicating  not  more  than  0.00112 
per  cent  N.) 

Determining  the  Value  of  Zinc  Dust.  —  Introduce  1  gm.  of  zinc  dust  together 
with  a  few  glass  beads  into  a  flask  of  about  200  c.c.  capacity,  closed  with  a  glass 
stopper,  and  then  add  a  mixture  of  30  c.c.  of  potassium  iodate  solution  and  100 
c.c.  of  sodium  hydroxide  solution  (potassium  iodate  solution:  15.25  gm.  KIO3,  to 
300  c.c.  H2O;  sodium  hydroxide  solution:  300  gm.  NaOH  to  1000  c.c.  H2O). 
Now  shake  the  contents  of  the  flask  vigorously  for  five  minutes;  transfer,  without 
filtering,  to  a  graduated  flask  of  1000  c.c.  capacity;  fill  with  water  up  to  the 
mark  and  mix.  Of  this  solution  transfer  100  c.c.  into  an  iodine  distillation 
apparatus.  Add  50  c.c.  of  diluted  sulphuric  acid,  and  after  expelling  the  air  by 
means  of  carbon  dioxide,  distil,  and  receive  the  iodine  in  potassium  iodide  solu- 
tion (1  :  5).  The  distillation  is  ordinarily  complete  in  about  twenty  minutes, 
and  may  be  recognized  by  the  contents  of  the  retort  having  become  colorless. 
The  iodine  distilled  over  is  titrated  with  decinormal  sodium  thiosulphate  solution. 
6I  =  15Zn.* 

1  c.c,  of  decinormal  Na2S2O3= 0.0163425  gm.  of  Zn,  log.  21332. 


ZINC   CHLORIDE 

ZnCl2.     Mol.  Wt.  136.29 

A  white  powder,  deliquescent  in  the  air,  and  easily  soluble  in 
water  and  in  alcohol.     The  aqueous  solution  is  acid  to  litmus  paper. 


*  15Zn+30NaOH-15Zn(ONa),+15H«. 
5KIO3  +  15H2  =  SKI  +  15H2O. 
KIO3 +5KI +3H2SO4  =  3K2SO4 +3H2O +61. 


184  CHEMICAL  REAGENTS 


TESTS   OF   PURITY 

Zinc  Oxychloride.  —  The  solution  of  1  gm.  of  zinc  chloride  in  1  c.c.  of  boiled 
water  should  be  clear,  or  at  most  only  slightly  turbid;  any  turbidity  caused  in 
the  solution  by  the  addition  of  3  c.c.  of  alcohol  (85  per  cent  by  weight)  should 
disappear  on  the  addition  of  0.05  c.c.  of  hydrochloric  acid.  (Indicating  less 
than  2.5  per  cent  as  ZnO.) 

Sulphates.  —  10  c.c.  of  the  1  :  10  aqueous  solution  acidulated  with  a  few  drops 
of  hydrochloric  acid  should  not  be  rendered  turbid  by  barium  chloride  solution. 
(Indicating  less  than  0.002  per  cent  SO3.) 

Foreign  Metals  and  Alkalies.  —  (a)  The  solution  of  1  gm.  of  zinc  chloride  in 
10  c.c.  of  water  acidulated  with  1  c.c.  of  hydrochloric  acid  should  appear  unchanged 
after  the  addition  of  hydrogen  sulphide  water.  (Indicating  no  foreign  metals 
present.) 

(6)  The  solution  of  1  gm.  of  zinc  chloride  dissolved  in  10  c.c.  of  water  should 
remain  clear  and  colorless  on  being  mixed  with  10  c.c.  of  ammonia  water.  On 
adding  5  drops  of  hydrogen  sulphide  water  to  the  solution,  a  pure  white  precipitate 
should  form.  (Indicating  no  foreign  metals  present.)  Precipitate  the  zinc 
completely  by  the  further  addition  of  hydrogen  sulphide  water.  On  filtering, 
evaporating  the  filtrate  to  dryness,  and  igniting,  no  weighable  residue  should 
remain.  (Indicating  less  than  0.05  per  cent  alkali  salts.) 


ZINC   IODIDE-STARCH   SOLUTION 

A  colorless,  clear,  or  only  slightly  opalescent  liquid.  It  deteri- 
orates with  age,  acquiring  a  blue  color. 

TESTS   OF  SENSITIVENESS 

A  mixture  of  1  c.c.  of  zinc  iodide-starch  solution  and  20  c.c.  of  water  should 
acquire  an  intense  blue  color  on  adding  1  drop  of  decinormal  iodine  solution. 

1  c.c.  of  zinc  iodide-starch  solution  diluted  with  50  c.c.  of  water  should  not 
acquire  a  blue  color  on  the  addition  of  diluted  sulphuric  acid. 


ZINC   OXIDE 
ZnO.     Mol.  Wt.  81.3^ 

A  white,  amorphous  powder,  having  a  faint  yellowish  tinge. 
Zinc  oxide  is  insoluble  in  water,  but  is  soluble  in  dilute  acetic  acid 
and  in  mineral  acids. 

TESTS  OF  PURITY 

Arsenic.  —  A  mixture  of  1  gm.  of  zinc  oxide  and  3  c.c.  of  stannous  chloride 
solution  should  not  acquire  a  darker  color  on  standing  one  hour.  (Indicating 
less  than  0.0015  per  cent  As.) 

Sulphates  and  Chlorides.  —  On  shaking  2  gm.  of  zinc  oxide  with  20  c.c.  of 
water  and  filtering,  the  filtrate  acidulated  with  nitric  acid  should  show  no  reaction 


ZINC  SULPHATE  185 

on  the  addition  of  barium  nitrate  solution,  and  should  acquire  at  most  a  slight 
opalescent  turbidity  on  the  addition  of  silver  nitrate  solution.  (Indicating  less 
than  0.0075  per  cent  SO3,  and  less  than  0.001  per  cent  Cl.) 

Nitrate.  —  Dissolve  1  gm.  of  zinc  oxide  in  10  c.c.  of  diluted  acetic  acid,  and 
add  1  drop  of  1  :  1000  indigo  solution,  a  small  crystal  of  sodium  chloride,  and 
10  c.c.  of  concentrated  sulphuric  acid.  The  blue  color  of  the  liquid  should  not 
disappear  on  shaking.  (Indicating  less  than  0.0016  per  cent  N2O6.) 

Carbonates,  Calcium,  Magnesium,  and  Foreign  Heavy  Metals.  —  1  gm.  ot 
zinc  oxide  should  dissolve  completely  in  10  c.c.  of  diluted  acetic  acid  withouf 
effervescence.  (Indicating  less  than  1  per  cent  CO2.)  On  adding  to  this  solution 
20  c.c.of  ammonia  water,  a  clear,  colorless  liquid  should  result  which  should  not 
show  a  change  on  the  addition  of  ammonium  oxalate  and  sodium  phosphate 
solutions  (indicating  less  than  0.02  per  cent  Ca  and  less  than  0.005  per  cent 
Mg),  and  which  should  give  a  pure  white  precipitate  with  5  drops  of  hydrogen 
sulphide  water.  (Indicating  no  foreign  heavy  metals  present.) 

Foreign  Bodies  which  Reduce  Permanganate  when  Zinc  Oxide  is  Dissolved 
in  Diluted  Sulphuric  Acid.  —  Very  carefully  triturate  3  gm.  of  zinc  oxide  in  a 
mortar  with  20  c.c.  of  water  containing  in  solution  0.2  gm.  of  pure  ferric  alum 
free  from  ferrous  salt.  Then  add  to  the  mixture  25  c.c.of  diluted  sulphuric  acid, 
and  effect  complete  solution  by  gently  heating.  Dilute  the  solution  with  100  c.c. 
of  thoroughly  boiled  and  cooled  water,  and  add  decinormal  potassium  permangan- 
ate solution.  One  drop  of  the  permanganate  solution  should  suffice  to  impart 
a  distinct  pink  color  to  the  solution.  (Indicating  none  present.) 


ZINC  SULPHATE 
ZnSO4+7H2O.    Mol.  Wt.  287.55 

Colorless  crystals,  efflorescent  in  dry  air,  soluble  in  0.6  part  of 
water,  and  almost  insoluble  in  alcohol.  The  aqueous  solution  is 
acid  to  litmus  paper. 

TESTS  OF  PURITY 

Chlorides.  —  The  1  :  20  aqueous  solution  should  not  be  affected  by  silver 
nitrate  solution.  (Indicating  less  than  0.001  per  cent  Cl.) 

Foreign  Metals.  —  0.5  gm.  of  zinc  sulphate  should  dissolve  in  a  mixture  of  10 
c.c.  of  water  and  5  c.c.  of  ammonia  water,  affording  a  clear  and  colorless  solution. 
This  solution  should  afford  a  pure  white  precipitate  with  5  drops  of  hydrogen 
sulphide  water.  (Indicating  none  present.) 

Iron.  —  1  gm.  of  zinc  sulphate  dissolved  in  20  c.c.  of  water  acidulated  with 
a  few  drops  of  nitric  acid  and  boiled  should  not  be  reddened  by  potassium  sul- 
phocyanate  solution.  (Indicating  less  than  0.0008  per  cent  Fe.) 

Nitrates.  —  Add  to  10  c.c.  of  a  1  :  10  zinc  sulphate  solution  1  drop  of  indigo 
solution,  a  small  crystal  of  sodium  chloride,  and  10  c.c.  of  concentrated  sulphuric 
acid.  The  blue  color  should  not  disappear  on  shaking.  (Indicating  less  than 
0.0016  per  cent  N2O5.) 

Ammonium  Compounds.  —  On  heating  1  gm.  of  zinc  sulphate  with  sodium 
hydroxide  solution,  no  vapors  of  ammonia  should  be  evolved  (to  be  ascertained 
by  moist  litmus  paper.  (Indicating  less  than  0.0035  per  cent  NH3.) 

Free  Sulphuric  Acid.  —  On  shaking  2  gm.  of  zinc  sulphate  with  10  c.c.  of 
85  per  cent  (by  weight)  alcohol,  and,  after  about  ten  minutes,  filtering,  the 


186  CHEMICAL  REAGENTS 


filtrate,  when  diluted  with  10  c.c.  of  water,  should  not  redden  blue  litmus  paper. 
(Indicating  none  present.) 

Arsenic.  —  Introduce  20  gm.  of  arsenic-free,  metallic  zinc  into  the  generating 
flask  of  a  Marsh  apparatus,  and  start  the  hydrogen  with  dilute  (1:5)  sulphuric 
acid.  Dissolve  2  gm.  of  zinc  sulphate  in  20  c.c.  of  water,  introduce  the  solution 
in  small  quantities  at  a  time  into  the  generating  flask  of  the  Marsh  apparatus. 
After  one  hour  no  deposit  of  arsenic  should  be  visible  within  the  reduction  tube. 
(Indicating  less  than  0.0005  per  cent  As.) 


INTERNATIONAL  ATOMIC  WEIGHTS 

1913 

INTERNATIONAL  ATOMIC  WEIGHTS 
O  =  16 


187 


Aluminum 

Al 

27  1 

Molybdenum      .  .  . 

Mo 

96  0 

Antimony      

Sb 

120.2 

Neodymium  

Nd 

144  3 

Argon 

A 

39  88 

Neon. 

Ne 

20  2 

Arsenic                

As 

74.96 

Nickel  

Ni 

58  68 

Barium        

Ba 

137.37 

Niton  (radium  emana- 

Bismuth                 .... 

Bi 

208.0 

tion)  

Nt 

222  4 

Boron.         

B 

11.0 

Nitrogen  

N 

14  01 

Bromine 

Br 

79  92 

Osmium   

Os 

190  9 

Cadmium 

Cd 

112  40 

Oxygen 

o 

16  00 

Caesium 

Cs 

132  81 

Palladium. 

Pd 

106  7 

Calcium. 

Ca 

40.07 

Phosphorus    

P 

31  04 

Carbon 

c 

12  00 

Platinum 

Pt 

195  2 

Cerium 

Ce 

140  25 

Potassium 

K 

39  10 

Chlorine  

Cl 

35.46 

Praseodymium  

Pr 

140  6 

Chromium 

Cr 

52  0 

Radium 

Rd 

226  4 

Cobalt 

Co 

58.97 

Rhodium  

Rh 

102  9 

Columbium  

Cb 

93.5 

Rubidium  

Rb 

85.45 

Copper 

Cu 

63  57 

Ruthenium.  .  . 

Ru 

101  7 

Dysprosium    

Dy 

162.5 

Samarium  

Sm 

150.4 

Erbium 

Er 

167  7 

Scandium. 

Sc 

44  1 

Europium      

Eu 

152.0 

Selenium  

Se 

79  2 

Fluorine 

F 

19  0 

Silicon 

Si 

28  3 

Gadolinium.        

Gd 

157.3 

Silver  

Ag 

107  88 

Gallium  

Ga 

69.9 

Sodium  

Na 

23.00 

Germanium  . 

Ge 

72  5 

Strontium. 

Sr 

87  63 

Glucinum  

Gl 

9.1 

Sulphur  

S 

32  07 

Gold 

Au 

197  2 

Tantalum 

Ta 

181  5 

Helium  

He 

3.99 

Tellurium  

Te 

127  5 

Holmium 

Ho 

163  5 

Terbium 

Tb 

159  2 

Hydrogen        

H 

1.008 

Thallium 

Tl 

204  0 

Indium  

In 

114.8 

Thorium  

Th 

232.4 

Iodine 

I 

126.92 

Thulium. 

Tm 

168  5 

Iridium  

Ir 

193.1 

Tin  

Sn 

119.0 

Iron 

Fe 

55.84 

Titanium 

Ti 

48  1 

Krypton 

Kr 

82.92 

Tungsten  

W 

184  0 

Lanthanum 

La 

139  0 

Uranium. 

u 

238  5 

Lead  

Pb 

207  .  10 

Vanadium  

V 

51  0 

Lithium 

Li 

6  94 

Xenon 

Xe 

130  2 

Lutecium 

Lu 

174.00 

Ytterbium  (Neoytter- 

^lagnesium 

Mg 

24  32 

bium) 

Yb 

172  0 

Manganese 

Mn 

54.93 

Yttrium      

Y 

89  0 

^lercury 

Hg 

200  6 

Zinc 

Zn 

65  37 

Zirconium.         

Zr 

90  6 

188  CHEMICAL  REAGENTS 

PREPARATION  OF  TEST  SOLUTIONS  COMMONLY  USED 


Test  Solution. 

Approx. 
Percentage 
Strength 
Generally 
Used. 

Quantity  of  Chemical 
Dissolved  in  Water  to 
Make  250  c.c. 

Approx. 
Normality 
Generally 
Used. 

Quantity  of  Chem- 
ical Dissolved  in 
Water  to  Make 
250  c.c. 

Acid  Acetic  

36     % 

90  gm.  (of  99  5  %acid) 

5  N 

75  gm    (of  99  5% 

Hydrobromic  

10% 

67  gm.  (of  40%  acid) 

0  5  N 

acid) 
25gm  (of40%acid) 

Hydriodic. 

10% 

60  gm    (of  acid  sp  gr 

0  5  N 

Hydrochloric 

31  9% 

1.5) 

5  N 

sp.gr.  1.5) 
120  gm    (of  acid 

Hydrosilicofluoric.  .  .  . 
lodic  . 

7.5% 
1  6% 

1.19) 
Acid  Hydrosilicofluoric 
(undiluted) 

0  5  N 

sp.gr.  1.19) 

Nitric 

10% 

5  N 

113  gm    (of  acid 

Nitro-hydrochloric  .  .  . 
Oxalic.    . 

10% 

1.40-1.42) 
62  c.c.  Acid  Nitric  sp. 
gr.  1.40-1.42  with  188 
c.c.  Acid  Hydrochloric 
sp.gr.  1.19 
25  gm 

1  58  N 

sp.gr.  1.40-1.  42) 
25  gm 

Phosphoric 

10% 

0  5  N 

Picric  

1% 

1.7) 
2  5  gm. 

0  043  N 

gr.  1.7) 
2.5  gm. 

Sulphuric  

95% 

Acid    Sulphuric    sp  gr 

Sulphuric 

10% 

1.84  (undiluted) 
28  gm     (of  acid  sp  gr 

5  N 

Sulphurous 

6% 

1.84) 

sp.gr.  1.84) 

Tartaric  >  
Amtnon.  Carbonate  

25% 
20% 

luted) 
70  gm. 
50   gm.    (with   50   c  c. 

3.7  N 

70  gm. 

Chloride  
Hydroxide  

Molybdate  

10% 
10%(NH«) 

Ammonia  Water,  10%) 
25  gm. 
90  gm.  (of  28%) 

18.75  gm.  Ammonium 

5  N 
5  N 

67  gm. 
75  gm.(of  Ammo- 
nia water,  28%) 

Oxalate 

4% 

Molybdate  in  125  c.c. 
Ammonia  Water,10% 
Pour  this  into  125  c.c. 
Acid  Nitric,  sp.gr.  1.2. 
10  gm 

0  5  N 

10  gm 

Sulphate  

10% 

25  gm. 

0.5  N 

8  gm. 

Sulphide  

Ammonium     Sulphide 

Polysulphide  

solution  (undiluted) 
Allow  the  colorless  am- 

Arsenous Oxide  

monium  sulphide  so- 
lution   to    stand    for 
some  time,  or  dissolve 
in  it  a  small  amount 
of  pure  sulphur. 
Saturated  solution 

0  25  N 

2  gm. 

Barium  Chloride  
Hydroxide 

10% 

Saturated 

25  gm. 
Barium     Hydroxide 

0.5  N 
0  2  N 

15  gm. 
32  gm. 

Nitrate 

solution 
10% 

Solution 
25  gm 

0  5  N 

16  gm 

Calcium  Chloride  

10% 

25  gm.   (of  crystals) 

0.5  N 

14  gm. 

Hydroxide  

0.14% 

0.35  gm.  (Lime  Water 

0.0378  N 

0.35  gm. 

Sulphate  

(saturated) 

undiluted) 
Saturated  solution 

Cobaltous  Nitrate  

10% 

25  gm. 

0.5  N 

18  gm. 

Cupric  Chloride  

4.4% 

11  gm. 

0.5  N 

11  gm. 

PREPARATION  OF  TEST  SOLUTIONS  COMMONLY  USED    189 
PREPARATION  OF  TEST  SOLUTIONS  COMMONLY   USED— Continued 


Test  Solution. 

Approx. 
Percentage 
Strength 
Generally 
Used. 

Quantity  of  Chemical 
Dissolved  in  Water  to 
Make  250  c.c. 

Approx. 
Normality 
Generally 
Used. 

Quantity  of  Chem 
ical  Dissolved  in 
Water  to  Make 
250  c.c. 

Cuprous  Chloride  
Ferric  Chloride  

2.4% 
10% 

6  gm. 
25  gm. 

0.5  N 
0  5  N 

6  gm. 

Ferrous  Sulphate  

6  8% 

17.5  gm.    (with  a  few 

0  5  N 

20  gm 

Hydrogen  Peroxide  
Lead  Acetate      

3% 
10% 

drops  H2SO4).     (Un- 
stable.) 
25  gm.  (of  30%) 
25  gm. 

0.5  N 

7  gm.  (of  30%) 

Magnesia  Mixture  

(1      c.c.  — 

Magnesium  Sulphate, 

Magnesium  Chloride  

0.01  gm.  P) 
5.2% 

25  gm. 
Ammonium  Chloride 
50  gm. 
Ammonia  Water  10%, 
105  c.c. 
Water,  200  c.c. 
13  gm. 

0.5  N 

\ 

13  gm. 

Sulphate  
Manganous  Chloride.  .  .  . 

10% 
4  8% 

25  gm. 
12  gm.   . 

0.5  N 
0.5  N 

16  gm. 
12.5  gm. 

Sulphate  
Mercuric  Chloride  
Nitrate 

6.8% 
5% 
60%  (with 

17  gm. 
12.5  gm. 
150  gm    Mercuric  Ni- 

0.5 N 
0.5  N 
0  5  N 

17  gm. 
20  gm 

Palladous  Sodium  Chloride. 
Potassium  Bromate  

11%  free 
acid) 
8.4% 
1.4% 

trate,    40    gm.    Acid 
Nitric  (sp.gr.  1.40-142) 
21  gm. 
3.5  gm. 

0.57  N 
0.5  N 

21  gm. 
3  .  5  gm. 

Bromide  

6% 

15  gm. 

0.5  N 

15  gm. 

Carbonate  

10% 

25  gm. 

3      N 

52  gm. 

Chloride 

3  6% 

9  gm. 

0.5  N 

9  gm. 

Chromate  
Dichromate  .... 
Ferrocyanide  .  .  . 
Ferricyanide.  .  .  . 
Hydroxide  

10% 
10% 
10% 
10% 

5% 

25  gm. 
25  gm. 
25  gm. 
25  gm. 
15  gm. 

0.5  N 
0.5  N 
0.5  N 
0.5  N 
5      N 

12  gm. 
6  gm. 
13  gm. 
14  gm. 
83  gm. 

lodate  
Iodide  
Nitrate 

1.78% 
20% 
5  2% 

4.46  gm. 
50  gm. 
13  gm. 

0.5  N 
0.5  N 
0.5  N 

4.5  gm. 
21  gm. 
13  gm. 

Permanganate.  . 

Thiocyanate.  .  .  . 
Sulphate  

/     0.32% 
\    (0.1  N) 
1%(0.1N) 

1% 

0.8  gm. 

2.5  gm. 
2.5  gm. 

0.5  N 

0.5N 

0.5  N 

4  gm. 

12  gm. 
11  gm. 

Platinic  Chloride  

13% 

33  gm. 

Silver  Nitrate  

f      1-6% 

4  gm. 

0.25  N 

11  gm. 

Sodium  Acetate    

\   (0.  1  N) 
10% 

25  gm. 

0.73  N 

25  gm. 

Carbonate  
Chloride 

16% 

2  8% 

40  gm.   (of  anhydrous 
salt) 
7  gm 

3      N 
0.5  N 

40  gm. 
7  gm. 

Hydroxide  

5% 

14  gm. 

5      N 

55  gm. 

Nitrate        

4  4% 

11  gm. 

0.5  N 

11  gm. 

Phosphate  
Sulphate  

Sulphide  

10% 
3.6% 

5%(Na2S) 

25  gm. 
9  gm. 

40  gm.  (Na2S+9H20) 

0.5  N 
0.5  N 

0.5  N 

15  gm. 
9  gm. 
f          15  gm. 
i  /"Mn_a  _l_qH20^ 

Sulphite  
Thiosulphate  
Stannous  Chloride  

6.4% 
\  2.4% 
\   (0.1  N) 
5  6% 

16  gm. 
6gm. 
14  gm. 

0.5  N 
0.1  N 
0.5N 

16  gm. 
6  gm. 
14  gm. 

Zinc  Chloride  

3  4% 

8.5  gm. 

0.5N 

8  .  5  gm. 

INDEX 


Acetic  Anhydride,  4 
Acetone,  1 
Acid  Acetic,  2,  3 

Acetic  Anhydride,  4 

Acetic,  Diluted,  30%,  4 

Acetic,  Glacial,  3 

Arsenous,  49 

Arsenous  Anhydride,  49 

Boric  Anhydride,  4 

Boric,  Fused,  4 

Carminic,  5 

Chloroplatinic,  121 

Chromic,  70 

Chromic  Anhydride,  70 

Citric,  6 

Gallic,  6 

Hydriodic,  7,  8 

Hydrobromic,  8 

Hydrochloric,  9,  11 

Hydrofluoric,  11 

Hydrosilicofluoric,  12 

lodic,  13 

lodic  Anhydride,  13 

Molybdic,  14 

Molybdic  Anhydride,  14 

Naphthionic,  15 

Naphthylaminesulphonic,  15 

Nitric,  15,  16,  17 

Nitric,  Crude,  17 

Nitric,  Fuming,  17 

Oxalic,  Crystals,  18 

Perchloric,  19 

Phosphomolybdic,  19 

Phosphoric  Anhydride,  21 

Phosphoric,  Ortho-,  20,  21 

Phosphotungstic,  21 

Picric,  22 

Picronitric,  22 

Pyrogallic,  148 

Rosolic,  23 

Succinic,  23 

Sulphanilic,  24 


Acid  Sulphuric,  24,  25 

Sulphuric  Anhydride,  26 

Sulphuric,  Diluted  (16%),  25 

Sulphuric,  Fuming,  27 

Sulphuric,  Fuming,  free  from  N,  26 

Sulphuric,  Fuming,  with  Phosphoric 
Anhydride,  28 

Sulphuric,     with     Phosphoric     An- 
hydride, 28 

Sulphurous,  28 

Sulphurous,  Cubes  for  Generating,  29 

Tannic,  29 

Tartaric,  30 

Thioacetic  Solution,  30 
Alcohol,  32,  33 

Absolute,  32 

Amylic,  31 

Ethylic,  32 

Methylic,  33 
Alphanaphthol,  34 
Aluminum  Oxide,  35 
Ammonia  Water,  36,  37 
Ammonio-Ferric  Alum,  98 
Ammonium  Acetate,  38 

Carbonate,  38 

Chloride,  39 

Chromate,  40 

Citrate  Solution,  40 

Dithiocarbonate  Solution,  41 

Fluoride,  41 

Molybdate,  42 

Molybdate  Solution,  42 

Nitrate,  43 

Oxalate,  43 

Persulphate,  44 

Phosphate,  44 

Sulphate,  45 

Sulphide  Solution,  46 

Sulphocyanate,  47 

Thioacetate  Solution,  47 
Amyl  Alcohol,  31 
Aniline,  48 

191 


192 


INDEX 


Antimony  Oxide,  48 

Arsenic  Trioxide,  49 

Asbestos,  Copper-Oxide,  49 

Asbestos,  Silver-,  49 

Atomic  Weights  of  1913,  Table  of,  187 

Azolitmin,  50 

Barium  Acetate,  50 

Carbonate,  50 

Chloride,  51 

Dioxide,  52 

Hydrate,  52 

Hydroxide,  52 

Hydroxide  Solution,  53 

Nitrate,  53 

Peroxide,  52 

Sulphide,  54 

Superoxide,  52 
Benzene,  54 
Benzidine,  55 

for  Blood  Test,  55 
Benzin,  56 

Petroleum,  56 
Benzol,  54 

Bismuth  and  Potassium  Iodide  Solu- 
tion, 57 

Subnitrate,  57 
Blood  Charcoal,  68 
Borax,  155 

Anhydrous,  156 

Glass,  156 
Boric  Anhydride,  4 
Boron  Trioxide,  4 
Bromine,  57 

Water,  58 
Brucine,  58 

Cadmium  and  Potassium  Iodide,  59 

Borotungstate  Solution,  59 
Calcium  Acid  Phosphate,  64 

Biphosphate,  64 

Carbonate,  60 

Chloride,  Crystals,  60 

Chloride,  Dry,  61 

Chloride,  Fused,  61 

Hydroxide,  62 

Oxide,  from  Iceland  Spar,  and  from 
Marble,  62 

Phosphate,  Dibasic,  63 

Phosphate,  Monobasic,  64 

Phosphate,  Primary,  64 

Phosphate,  Secondary,  63 

Phosphate,  Tertiary,  64 

Phosphate,  Tribasic,  64 

Sulphate,  65 

Sulphide,  65 


Calcium  Superphosphate,  64 
Carbon  Disulphide,  66 

Tetrachloride,  66 
Carmine,  67 
Carmine-Fibrin,  67 
Caustic  Potash,  135 
Caustic  Soda,  160,  161,  162 

Soda  Solutions,  163 
Charcoal,  Animal,  68 
Chlorine  Water,  69 
Chloroform,  69 
Chromic  Anhydride,  70 
Chromium   Trioxide,    free   from    Sul- 
phuric Acid,  70 

Trioxide  for  Carbon  Determination, 

70 
Cobalt  Nitrate,  71 

Nitrate,  free  from  nickel,  72 

Oxide,  72 
Collodion,  72 
Copper  and  Ammonium  Chloride,  77 

by  Electrolysis,  73 

Chloride,  Cupric,  73 

Chloride,  Cuprous,  74 

Dichloride,  73 

Hydroxide,  74 

Monochloride,  74 

Oxide,  75,  76 

Oxide  Asbestos,  49 

Sulphate,  76 
Corallin,  23 
Corrosive  Sublimate,  112 

Devarda's  Metal  (or  Alloy),  77 

Diacetyl-dioxime,  78 

Dicalcium  Phosphate,  63 

Dicyandiamidine  Sulphate,  78 

Dimethylglyoxime,  78 

.  Dimethylparaphenylenediamine     Hy- 

drochloride,  79 
Diphenylamine,  79 

Solution,  79 

Diphenylendanilodihydrotriazol,  116 
Disodium  Hydrogen  Phosphate,  170 

Ether,  80 

Anhydrous,  81 
Petroleum,  56 

Ferric  Ammonium  Sulphate,  98 
Ferrous  Ammonium  Sulphate,  98 
Furfural,  81 
Furfurol,  81 

Gallein,  Dry,  82 
Glass  Wool,  82 


INDEX 


193 


Glycerin,  82,  83 
Guaiacin,  84 
Gypsum,  65 

Hematein,  84 
Hematoxylin,  84 
Hide  Powder,  85 
Hydrazine  Sulphate,  85 
Hydrogen  Peroxide,  30%,  86 

Sulphide  Water,  87 
Hydroxylamine  Hydrochloride,  87 

Indigo  Carmine,  165 

Solutions,  1 :40  and  1 :1000,  89 

Synthetic  and  Vegetable,  88 
lodeosin,  89 
lodic  Anhydride,  13 
Iodine,  90 

Water,  90 
Iron,  90 

and  Ammonium  Sulphate,  Ferric,  98 

and  Ammonium  Sulphate,  Ferrous, 
98 

by  Hydrogen,  92 

Chloride,  Ferric,  93 

Chloride,  Ferric,  Solution,  94 

Chloride,  Ferrous,  94 

Oxide,  95 

Powder,  93 

Reduced,  92 

Sulphate,  Ferrous,  97 

Sulphide,  97 

Wire,  91 

Lacmoid.  99 
Lead  Acetate,  99 

Chromate,  100 

Dioxide,  101 

Oxide,     Brown,     for     Dennstedt's 
Analysis,  102 

Oxide,     Brown,     free    from     Man- 
ganese, 101 

Oxide,  Brown,  Granulated,  102 

Oxide,  Yellow,  103 

Peroxide,  101 

Subacetate  Solution,  103 

Superoxide,  101 
Lime,  Chlorinated,  104 

Slaked,  62 

Sulphurated,  65 

Water,  104 
Litharge,  103 
Litmus,  104 

Magnesia,  107 
Mixture,  105 


Magnesite,  105 

Magnesium  and  Ammonium  Chloride, 
109 

Carbonate,  105 

Chloride,  106 

Oxide,  107 

Oxide,  free  from  Sulphates,  108 

Sulphate,  108 
Manganese  Chloride,  109 

Dioxide,  110 

Metaphosphate  Solution,  111 

Peroxide,  110 

Sulphate,  111 

Superoxide,  110 
Manganous  Chloride,  109 
Marignac's  Salt,  144 
Mercuric  Chloride,  112 

-Potassium  Iodide,  114 
Mercury,  111 

and  Potassium  Iodide,  114 

Bichloride,  112 

Nitrate  (ous),  112 

Oxide,  Red,  113 

Oxide,  Yellow,  114 
Metadiaminobenzene     Hydrochloride, 

114 
Metaphenylenediamine  Hydrochloride, 

114 
Methyl  Alcohol,  33 

Alcohol-Hydrochloric  Acid,  4 

Orange,  115 

Red,  115 

Microcosmic  Salt,  175 
Mohr's  Salt,  98 
Molybdic  Anhydride,  14 
Monocalcium  Phosphate,  64 

Nitrobenzaldehyde,  Ortho-,  115 
Nitron,  116 

Nitrophenol,  Ortho-,  117 
Nitrophenol,  Para-,  117 
Nitrosobetanaphthol,  117 

Palladium,  117 

and  Sodium  Chloride-,  119 

Chloride  (ous),  118 

Nitrate  (ous),  118 
Para-aminodimethylaniline  Hydro- 
chloride,  79 

Paradiaminodiphenyl,  55 
Paratetramethylphenylenediamine 

Hydrochloride,  176 
Perhydrol,  86 
Petroleum  Benzin,  56 

Ether,  56 
Phenacetolin,  119 


194 


INDEX 


Phenolphthalein,  119 
Phenylhydrazine,  120 
Phloroglucin,  120 
Phosphoric  Anhydride,  21 
Platinum,  121 

Chloride  (ic),  121 
Poirrier's  Blue  C  4  B,  122 
Potassium  Acetate  Solution,  122 

Acid  Pyroantimonate,  123 

Acid  Sulphate,  125 

Acid  Sulphite,  126 

Acid  Tartrate,  126 

and  Sodium  Tartrate,  147 

Antimonate,  123 

Bicarbonate,  123 

Biniodate,  124 

Bisulphate,  125 

Bisulphite,  Meta,  126 

Bitartrate,  126 

Bromate,  127 

Bromide,  128 

-Cadmium  Iodide,  59 

Carbonate,  128 

Carbonate  Solution,  129 

Chlorate,  130 

Chloride,  131 

Chromate,  131 

Cyanide,  132 

Bichromate,  133 

Ferricyanide,  133 

Ferrocyanide,  134 

Hydrate,  135 

Hydrosulphide,  146 

Hydroxide,  Pure,  136 

Hydroxide,  Purest,  135 

Hydroxide,  Purified,  137 

Hydroxide  Solutions,  138 

lodate,  138 

Iodide,  139 

Iodide,  Neutral,  139 

Nitrate,  140 

Nitrite,  140 

Oxalate,  Neutral,  141 

Perchlorate,  142 

Permanganate,  142 

Permanganate,  free  from  sulphates, 
143 

Persulphate,  143 

Pyroantimonate,  Acid,  123 

Stannosulphate,  144 

Sulphate,  144 

Sulphide,  145 

Sulphide  Solution,  145 

Sulphocyanate,  146 

Sulphydrate,  146 

Tetraoxalate,  147 


Potassium  Thiocyanate,  146 
Prussiate  of  Potash,  Red,  133 

of  Potash,  Yellow,  134 
Pumice  Stone,  Platinized,  148 
Pyrogallol,  148 
Pyrolusite,  110 

Quartz  Sand,  148 

Resorcin,  149 
Resorcinol,  149 

Blue,  99 
Rochelle  Salt,  147 

Schiff's  Reagent,  47 
Sea  Sand,  149 
Seignette  Salt,  147 
Silver,  149 

-Asbestos,  49 

Nitrate,  150 

Nitrite,  151 
Soda,  Caustic,  160,  161,  162 

-Lime,  164 
Sodium,  151 

Acetate,  151 

Acid  Sulphate,  153 

Acid  Sulphite,  154 

Amalgam,  152 

and  Ammonium  Phosphate,  175 

and   Potassium   Carbonate.   Fused. 
176 

Biborate,  155 

Bicarbonate,  152 

Bisulphate,  153 

Bisulphite,  154 

Borate,  155 

Borate,  Calcined,  156 

Borate,  Fused,  156 

Bromate,  157 

Carbonate,  157 

Carbonate,  Anhydrous,  158 

Chloride,  159 

Chloride,  Fused,  160 

-Cobaltic  Nitrite  Solution,  176 

Hydrate,  160,  161,  162 

Hydroxide,  160,  161,  162 

Hydroxide  Solutions,  163,  164 

Hydroxide  with  Lime,  164 

Hydroxide  with  Lime  from  Iceland 
Spar,  164 

Hyposulphite,  174 

Indigo  tinsulphonate,  165 

Nitrate,  165 

Nitrite,  166 

Nitrite,  free  from  Potassium,  167 

Nitroferricyanide,  167 


INDEX 


195 


Sodium  Nitroprusside,  167 

Oxalate,  167 

-Palladous  Chloride,  119 

Peroxide,  169 

Phosphate,  170 

Phosphate,  Secondary,  170 

Pyrophosphate,  171 

Sulphate,  171 

Sulphide,  172 

Sulphide  Solution,  172 

Sulphite,  Crystals  and  Dried,  173 

Superoxide,  169 

Tetraborate,  155 

Thiosulphate,  174 

Tungstate,  175 

Wolframate,  175 
Solution  Acid  Thioacetic,  30 

Ammonium  Citrate,  4J 

Ammonium  Dit  hie  carbonate,  41 

Ammonium  Molybdute,  42 

Ammonium  Sulphide,  46 

Ammonium  Thioacet  1e;  47 

Barium  Hydroxide,  53 

Bismuth  and  Pot  ssium  Iodide,  57 

C  dmium  Borotungstate,  59 

Iron  Chloride,  Ferric,  94 

Lead  Subacetate,  103 

Manganese  Metaphosphate,  111 

Potassium  Acetate,  122 

Potassium  Carbonate,  129 

Potassium  Hydroxide,  138 

Potassium  Sulphide,  145 

Silver    Nitrate,  Ammoniacal   (foot- 
note), 1,  32,  56 

Sodium-Cobaltic  Nitrite,  176 

Sodium  Hydroxide,  I  and  II,  free 
from  Nitrogen,  163 

Sodium  Hydroxide,  III,  164 


Solution  Sodium  Sulphide,  172 

Stannous  Chloride,  178 

Tin  Chloride,  178 

Zinc  Iodide-Starch,  184 
Sorensen's  Oxalate,  167 
Sulphuric  Anhydride,  26 

Table  of  Atomic  Wreights  of  1913,  187 
Tannin,  29 

Test  Solutions  Commonly  used,  Prep- 
aration of,  188 
Tetraiodofluorescein,  89 
Tetramethylparaphenylenediamine 

Hydrochloride,  176 
Thymol,  176 
Tin,  177 

Chloride,  178 

CliLr.de  S  la.ion,  178 
Trie  Icium  Ph  sphate,  64 
Triuitrjphe^ol,  ^J, 

Uranium  Ace  Late,  179 

Acetate,  free  from  Sodium,  179 
Nitrate,  180 

Water,  Distilled,  180 
Xylidine,  181 

Zinc  Chloride,  183 ' 
Dust,  183 
free  from  As,  182 

free  from  As,  nearly  free  from  Fe,  182 
free  from  As,  S,  P,  and  Fe,  181 
Iodide-Starch  Solution,  184 
Oxide,  184 
Sulphate,  185 


INDEX  OF  AUTHORS 


Adler,  A.  (Benzidine),  56 
Adler,  O.  (Benzidine),  56 
Allen  (Alcohol),  32;  (Hide  Powder),  85; 

(Methyl      Alcohol),  34;     (Tannic 

Acid),  30. 

Andersen  (Sodium  Oxalate),  169 
Ascarelli,  A.  (Benzidine),  56 

Baeyer,  A.  (Phloroglucin),  120 

Barbel,  M.  E.  (Alcohol),  32 

Barbieri,  J.  (Copper  Hydroxide),  74 

Berl,  E.  (Nitron),  116 

Biltz,  A.  (Nitron),  116 

Blume,  G.  (Nitron),  116 

Blum,  L.  (Manganese  Metaphosphate), 

111 

Bockmann  (Gallein),  82 
Bogolubow,  P.  (Dimethylglyoxime),  79 
Bogomoloff,  T.  J.  (Carminic  Acid),  5 
Brandt,  L.  (Iron  Oxide),  95 
Brunck,  O.  (Cobalt  Oxide),  72;    (Di- 

methylfflyoxime),  79 
Bucket,  M.  '(Citric  Acid),  6 
Busch,  M.  (Nitron),  116 

Cailletet  (Citric  Acid),  6 
Carletti,  O.  (Furfural),  81 
Cazeneuve,  P.  (Alcohol),  52 
Cimmino,  R.  (Diphenylamine),  70 
.Cohn  (Phenacetolin),  119 
Cormack,  W.  (Furfural),  81 
Craandijk,  M.  M.  (Amyl  Alcohol),  31 
Crismer,  M.  L.  (Citric  Acid),  6  ' 

Davidson,    E.    (Potassium   Chlorate), 

130 

Dechan,  H.  (Gallein),  82 
Dennstedt,  M.  (Lead  Oxide,  Brown), 

102 

Devarda,  A.  (Devarda's  Metal),  78 
Diethelm,  B.  (Lead  Oxide,  Brown),  102 
Dimroth,  O.  (Carminic  Acid),  5 


Donath,  E.  (Carmine),  67 
Diirkes,  K.  (Benzidine),  55 

Eggers,  E.  (Furfural),  81 
Einhorn,  M.  (Benzidine),  56] 
Engel,  R.  (Poirrier's  Blue),  122 
Erdman,  H.  (Palladium),  118 

Falco,  F.  (Palladium),  118 

Fassbender,  G.  (Copper  Hydroxide),  74 

Feitler,  S.  (Carmine),  67 

Foerster,  P.  (Platinum),  121 

Frank,  F.  (Benzidine),  55 

Franzen,  H.  (Nitron),  116 

Fresenius    (Palladium),  118;     (Tannic 

Acid),  30 
Fresenius-Cohn       (Palladium),      118; 

(Tannic  Acid),  30 
Friedheim  (Benzidine),  55 

Ganghofer,  A.  (Nitron),  117 

Gerber,  N.  (Amyl  Alcohol),  31 

Glaser  (Phenacetolin),  119 

Gould  (Carmine),  67 

Grossmann,  H.  (Dicyandiamidine  Sul- 
phate), 78 

Grutzner,  P.  (Carmine-fibrin),  68 

Gutbier,  A.  (Nitron),  116;  (Palladium), 
118 

Gutman,  A.  (Sodium  Thiosulphate), 
174 

Hassler,  F.  (Lead  Oxide,  Brown),  102 
Heidenreich  (Boric  Anhydride),  4 
Heilbron,    W.    (Dicyandiamidine  Sul- 
phate), 78 

Hermann,  H.  (Lead  Oxide,  Brown),  102 
Hes,  A.  (Nitron),  116 
Holmes,  J.  (Alcohol),  33 
Hoist,  F.  (Benzidine),  56 
Horing,  P.  (Carminic  Acid),  5 

197 


198 


INDEX  OF  AUTHORS 


Hiibener,  G.   (Sodium  Thiosulphate), 
174 

Isler  (Sulphuric  Acid),  25 

Jannasch,  P.  (Boric  Anhydride),  4 
Jolles,   A.    (Dimethylparaphenylenedi- 
amine  Hydrochloride),  79 

Katz  (Hydrofluoric  Acid),  11;  (Hydro- 

silicofluoric  Acid),  13 
Kehrmann,  F.  (Phosphotungstic  Acid), 

22 
Kippenberger,  C.   (Hematoxylin),  84; 

lodeosin),  89;  (Lacmoid),  99 
Knorre,  G.  (Benzidine),  55 
Kohn,  S.  (Hydrosilicofluoric  Acid),  13 
Kolb,  A.  (Potassium  Chlorate),  130 
Komarowsky,  A.  (Furfural),  81 
Korn,  A.  (Carmine-Fibrin),  68 
Kramer,  G.  (Methyl  Alcohol),  34 
Kraut,  K.  (Dimethylglyoxime),  79 

Landau,  J.  (Carminic  Acid),  5 
Landolt-Bornstein-Roth  (Acetic  Acid), 
3;    (Hydrochloric  Acid),  10;    (Ni- 
tric Acid),  15;    (Sulphuric  Acid), 
25 

Lang  (Alcohol),  32 
Lewkowitsch  (Furfural),  81 
Liebermann,  C.  (Carminic  Acid),  5 
Lindenbaum,  S.  (Carminic  Acid),  5 
Litzendorff,  J.  (Nitron),  116 
Lohmann,  E.  (Nitron),  116 
Loose,  R.  (Methyl  Red),  115 
Lunge,  G.  (Acetic  Acid),  3;   (Alcohol), 
32;     (Aniline),    48;      (Devarda's 
Metal),  78;  (Diphenylamine),  79; 
(Hydrochloric    Acid),    10;    (Iron 
Wire),  91,  92;  (Manganese  Diox- 
ide), 110;  (Methyl  Alcohol),    34; 
(Nitric  Acid),  15;   (Nitron),   116; 
(Sodium  Carbonate),  158;    (Sodi- 
um Oxalate),  169;  (Sodium  Per- 
oxide), 170;   (Sulphuric  Acid),  25, 
27;   (Tannic  Acid),  30 

Makowka,  O.  (Palladium),  118 
Malerba,  H.  N.  (Dimethylparaphenyl- 

enediamine  Hydrochloride),  79 
Marchlewski,  L.   (Carminic  Acid),  5; 

(Hydrochloric  Acid),  10 
Mehrtens,  G.  (Nitron),  116 
Meissel  (Devarda's  Metal),  78 
Meissner,  O.  (Lead  Oxide,  Brown),  102  , 
Merck  (lodeosin),  89 


Merkel,  H.  (Benzidine),  56 
Messerschmidt,  Th.  (Benzidine),  56 
Messinger,  J.  (Methyl  Alcohol),  34 
Messner,  J.  (Herratoxylin),  84;    (Lac- 
moid),  99;   (Porrier's  Blue),  122 
Miller,    O.     (Indigo),    88;      (Sodium 

Indigotinsulphonate) ,  1 65 
Mohr,  F.  (Arsenic  Trioxide),  49 
Muller,  E.  (Lead  Oxide,  Brown),  102 
Miiller,  Wolf  J.  (Benzidine),  55 
Muth,  W.  (Aluminum  Oxide),  35 
Mylius,  F.  (Platinum),  121 

Naef  (Sulphuric  Acid),  25 
Nydegger  (Benzidine),  55 

Paal,  C.  (Nitron),  116,  117 

Pabst,  M.  (Dimethylparaphenylene- 
diamine  Hydrochloride),  79 

Porth,  P.  (Nitron),  116 

Pregl,  F.  (Copper  Oxide  Asbestos),  49; 
(Silver  Asbestos),  49;  (Lead  Ox- 
ide, Brown),  102 

Proctor  (Hide  Powder),  85 

Radcliffe,     L.     G.     (Carbon     Tetra- 

chloride),  67 

Radlberger,  L.  (Nitron),  116 
Raschig  (Benzidine),  55 
Riegler,  E.    (Naphthylaminesulphonic 

Acid),  15 
Ritthausen,  C.  H.  L.  (Lead  Chromate), 

100 
Rosenlecher,  R.  (Sulphuric  Anhydride), 

Rupp,  E.  (Mercuric  chloride),  112; 
(Methyl  Red),  115 

Salzer  (Citric  Acid),  6 

Schiff,  H.  (Furfural),  81 

Schiff,  R.  (Ammonium  Thioacetate), 
48;  (Thioacetic  Acid),  30 

Schlesinger,  E.  (Benzidine),  56 

Schmitt  (Guaiacin),  84 

Schmitz-Dumont  (Carbon  Tetrachlo- 
ride),  67 

Schiick,  B.  (Dicyandiamidine  Sul- 
phate), 78 ' 

Schultz,  G.  (Aniline),  48 

Schulze,  E.  (Copper  Hydroxide),  74 

Schumm,  O.  (Benzidine),  56 

Schunck,  E.  (Carminic  Acid),  5 

Schwalbe,  C.  (Benzene),  54 

Smirnoff,  J.  (Indigo),  88;  (Sodium 
Indig-t'nsulphmite),  165 


INDEX  OF  AUTHORS 


199 


Sorensen,  S.  P.  L.  (Sodium  Oxalate), 

168,  169 

Spindler,  O.  (Citric  Acid),  6 
Stone,  W.  E.  (Furfural),  81 
Strache,  H.  (Methyl  Alcohol),  34 
Stutzer,  A.  (Copper  Hydroxide),  74 
Sutton  (Arsenic  Trioxide),  49 

Tarugi,  N.  P.  (Ammonium  Thioace- 
tate),  48;  (Thioacetic  Acid),  30 

Tatlock  (Citric  Acid),  6;  (Potassium 
Bitartrate),  127;  (Tartaric  Acid), 
30 

Thompson  (Citric  Acid),  6;  (Potas- 
sium Bitartrate),  127;  (Tartaric 
Acid),  30 

Thorpe,  T.  E.  (Alcohol),  33;  (Aniline), 
48;  (Sulphuric  Acid,  Fuming),  27 

Tizard  (Methyl  Red),  115 

Traube,  W.  (Nitron),  116 

Tschugaeff,  L.  (Dimethylglyoxime),  79 

Utz,  F.  (Benzidine),  56;  (Furfural),  81 


Visser,  H.  L.  (Nitron),  116 
Vogtherr,     M.     (Ammonium    Dithio- 

carbonate  Solution),  41 
Voswinckel,  H.  (Carminic  Acid),  5 


Walter,  E.  (Benzidine),  56 
Wassilieff,  N.  J.  (Carminic  Acid),  5 
Watt  (Aniline),  48 
Weidenkafif,  E.  (Nitron),  116 
Weil,  H.  (Lead  Oxide,  Brown),  102 
Wender,  N.  (Furfural),  81 
Wesseley,  L.  (Hydrosilicofluoric  Acid), 

Westphal,  C.  (Benzidine),  56 
White,  F.  W.  (Benzidine),  56 
Wiedemann,  F.  (Carminic  Acid),  5 
Wislicenus,  H.  (Aluminum  Oxide),  35 
Weltering  (Furfural),  81 
Wurster,  C.  (Dimethylparaphenylene- 
diamine  Hydrochloride),  79;   (Te- 
tramethylparaphenylenediamme 
Hydrochloride),  176 


UN" 


TF 


3CJ29 


Df/ 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


